Please refer to the attached screenshot and sample project.

Workaround: call the RadForm.EndInit method before showing the form.

To reproduce:

public partial class RadRibbonForm1 : Telerik.WinControls.UI.RadRibbonForm
    {
        public RadRibbonForm1()
        {
            InitializeComponent();
            this.AllowAero = true;
            this.RibbonBar.QuickAccessToolbarBelowRibbon = false;
        }
    }

Note: the system buttons not always handle the mouse click.

Workaround: set AllowAero to false OR RibbonBar.QuickAccessToolbarBelowRibbon to true.

To reproduce: Please refer to the attached screenshots and sample project:

1. Disable Aero
2. Change to Windows Classic
3. Run the provided project

Workaround: change to Windows 7 aero Theme with disabled transparency.

The attached video shows how you can reproduce this.

The issue is easily reproducible on a remote Windows 7 machine.

To reproduce:

public Form1()
{
    InitializeComponent();
    this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
}

Although the user is not allowed to resize the form from the form's borders, it is possible to do it by the context menu.

Workaround:

[DllImport("user32.dll")]
static extern bool EnableMenuItem(IntPtr hMenu, uint uIDEnableItem, uint uEnable);

internal const UInt32 MF_DISABLED = 0x00000002;

internal const UInt32 SC_SIZE = 0xF000;

internal const UInt32 WM_INITMENUPOPUP = 0x0117;

protected override void WndProc(ref Message m)
{
    if (m.Msg == WM_INITMENUPOPUP && (((int)m.LParam & 0x10000) != 0))
    {
        EnableMenuItem(m.WParam, SC_SIZE, MF_DISABLED);
    }

    base.WndProc(ref m);
}

To reproduce:
Use the following method to add a form with a textbox to a panel:
Private Sub AddPage(ByRef f As Form)
    Try
        pnlScreenContainer.SuspendUpdate()
        f.TopLevel = False
        f.Visible = False
        f.Dock = DockStyle.Fill
        pnlScreenContainer.Controls.Add(f)
        f.Visible = True
        f.BringToFront()
        f.FormBorderStyle = Windows.Forms.FormBorderStyle.None
        f.Show()

        f.Activate()
    Catch
    End Try
    pnlScreenContainer.ResumeUpdate()
End Sub

Workaround:
- Use RadTextBoxControl instead.

To reproduce: add a RadForm and start the application.

Workaround:
public partial class Form1 : RadForm
{
    public Form1()
    {
        InitializeComponent();
        
    }

    protected override void OnLoad(Size desiredSize)
    {
        this.ElementTree.InitializeRootElement();
        this.RootElement.ApplyShapeToControl = false;
        base.OnLoad(desiredSize);
    }

    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        this.RootElement.ApplyShapeToControl = true;
    }
}

How to reproduce: 
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.IsMdiContainer = true;
        this.Load += Form1_Load;
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        RadForm form = new RadForm();
        form.Text = "MDI Child 1";
        form.MdiParent = this;
        form.Show();
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        RadForm activeChild = this.ActiveMdiChild as RadForm;
        if (activeChild == null)
        {
            MessageBox.Show("no active form child found!");
            return;
        }
        else
        {
            SaveAsBitmap(activeChild, activeChild + ".Jpeg");
            MessageBox.Show("Screen Captured successfully.");
        }
    }

    public void SaveAsBitmap(Form form, string fileName)
    {
        SaveFileDialog dialog = new SaveFileDialog();
        dialog.Filter = "JPeg Image|*.jpg|Bitmap Image|*.bmp|Gif Image|*.gif";
        if (dialog.ShowDialog() == DialogResult.OK)
        {
            Bitmap bmp = new Bitmap(form.Width, form.Height);
            form.DrawToBitmap(bmp, new Rectangle(0, 0, form.Width, form.Height));
            bmp.Save(dialog.FileName, ImageFormat.Jpeg);
        }
    }
}

Workaround:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.IsMdiContainer = true;
        this.Load += Form1_Load;
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        RadForm form = new RadForm();
        form.Text = "MDI Child 1";
        form.MdiParent = this;
        form.Show();
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        RadForm activeChild = this.ActiveMdiChild as RadForm;
        if (activeChild == null)
        {
            MessageBox.Show("no active form child found!");
            return;
        }
        else
        {
            SaveAsBitmap(activeChild, activeChild + ".Jpeg");
            MessageBox.Show("Screen Captured successfully.");
        }
    }

    public void SaveAsBitmap(Form form, string fileName)
    {
        Bitmap bmpScreenshot = new Bitmap(form.Bounds.Width, form.Bounds.Height, PixelFormat.Format32bppArgb);
        Graphics gfxScreenshot = Graphics.FromImage(bmpScreenshot);
        Point pt = form.Parent.PointToScreen(form.Location);
        gfxScreenshot.CopyFromScreen(pt.X, pt.Y, 0, 0, form.Bounds.Size, CopyPixelOperation.SourceCopy);
        SaveFileDialog saveImageDialog = new SaveFileDialog();
        saveImageDialog.Title = "Select output file:";
        saveImageDialog.Filter = "JPeg Image|*.jpg|Bitmap Image|*.bmp|Gif Image|*.gif";
        if (saveImageDialog.ShowDialog() == DialogResult.OK)
        {
            bmpScreenshot.Save(saveImageDialog.FileName, ImageFormat.Png);
        }
    }
}

To reproduce:
- Add RadMenu to a panel which is docked to the top.
- Add an MDI child and maximize it.
- You will notice that there is one more set of form buttons visible.

Workaround:
- Leave the menu outside of the panel.

To reproduce: 
- Set the MaximizedBounds property so the form takes the entire right part of the screen, the change the windows state at runtime:
private void radButton1_Click(object sender, EventArgs e)
{
    setFormMaximizedBounds(200);
}

private void radButton2_Click(object sender, EventArgs e)
{
    setFormMaximizedBounds(-1);
}
private void setFormMaximizedBounds(int distance)
{
    if (distance >= 0)
    {
        var ownerScreen = Screen.FromControl(this);
        var workingArea = ownerScreen.WorkingArea;
        var x = workingArea.X + distance;
        var y = workingArea.Y;
        var w = workingArea.Width - distance;
        var h = workingArea.Height;
        this.MaximizedBounds = new Rectangle(x, y, w, h);
    }
    else
    {
        this.MaximizedBounds = new Rectangle(0, 0, 0, 0);
    }

    if (this.WindowState == FormWindowState.Maximized)
    {
        this.WindowState = FormWindowState.Normal;
        this.WindowState = FormWindowState.Maximized;
    }
}

To reproduce: use the following code snippet:

public Form1()
{
    InitializeComponent();

    this.radDropDownList1.SelectedIndexChanged+=radDropDownList1_SelectedIndexChanged;
    this.radDropDownList1.Items.Add("TelerikMetro");
    this.radDropDownList1.Items.Add("Windows8");
    this.radDropDownList1.Items.Add("VisualStudio2012Dark");

    this.radDropDownList1.SelectedIndex = 1;

    this.SizeChanged+=Form1_SizeChanged;
}

private void radDropDownList1_SelectedIndexChanged(object sender, Telerik.WinControls.UI.Data.PositionChangedEventArgs e)
{
    ThemeResolutionService.ApplicationThemeName = this.radDropDownList1.Text;
}

1. Use two monitors and decrease the screen resolution to the main monitor.
2. Run the application from the first monitor and move the form to the second monitor.
3. Resize the form on a way to increase the form's height to be greater than the height of the screen resolution of the main monitor.
4. Change the theme. You will notice that that form is resized.

Workaround:

public Form1()
{
    InitializeComponent();

    this.radDropDownList1.SelectedIndexChanged += radDropDownList1_SelectedIndexChanged;
    this.radDropDownList1.Items.Add("TelerikMetro");
    this.radDropDownList1.Items.Add("Windows8");
    this.radDropDownList1.Items.Add("VisualStudio2012Dark");

    this.radDropDownList1.SelectedIndex = 1;

    this.SizeChanged += Form1_SizeChanged;
}

private void Form1_SizeChanged(object sender, EventArgs e)
{
    if (fSize != Size.Empty)
    {
        this.SizeChanged-= Form1_SizeChanged;
        this.Size = fSize;
        
        this.SizeChanged += Form1_SizeChanged;
    }
}

Size fSize = Size.Empty;

private void radDropDownList1_SelectedIndexChanged(object sender, Telerik.WinControls.UI.Data.PositionChangedEventArgs e)
{
    fSize = this.Size;
    ThemeResolutionService.ApplicationThemeName = this.radDropDownList1.Text;
    fSize=Size.Empty;
}

If you have an MDI form with controls anchored to bottom-left, and if the form is shown the following way:

Form form = new ChildForm()
form.MdiParent = this;
form.Show();

private void ChildForm_Load(object sender, EventArgs e)
{
         this.ThemeName = "Office2007Black";
}

the anchored controls will be misplaced.

WORKAROUND:

either set the parent after show:
Form form = new ChildForm()
form.Show();
form.MdiParent = this;

or do not use the Load event to apply theme - use the constructor or the Shown event:

public ChildForm()
{ 
         InitializeComponent();
         this.ThemeName = "Office2007Black";
}

To reproduce:
- Add form and set its AutoScroll property to true. add some controls so the scrollbars appear.
- Dock the form in a smaller window as a MDI child.

Workaround -  Use scrollable panel.

When you have a RadPageViewPage with a TableLayoutPanel inside a RadForm, by changing the theme the TableLayoutPanel is shrinking.

Pleas find attached a sample project.

Workaround: use a ShapedForm instead of RadForm/RadRibbonForm.

Workaround: set the RadRibbonFormBehavior1.AllowTheming property of the form to false

public class RadForm1
{
	public RadForm1()
	{
		InitializeComponent();

		this.RadRibbonFormBehavior1.AllowTheming = false;

	}
}

To reproduce:

public Form1()
{
    InitializeComponent();

    RadMessageBox.Instance.AutoSize = true;
}

private void radButton1_Click(object sender, EventArgs e)
{
    string msg = string.Format("Test", (sender as RadButton).Name);
    RadMessageBox.Show(msg, "Error");
}

Note that the size of  RadMessageBox is adjusted automatically to display the whole content. Hence, it is not necessary to set the RadMessageBox.Instance.AutoSize property to true.

For the time being to show the grid I would recommend you to use an empty RadStatusStrip.

Please refer to the attached screenshot.

Workaround: use a RadForm without RadRibbonFormBehavior and hide the FormElement.TitleBar.