To reproduce:
-Add RadBrowseEditor to a form and set the DialogType to FolderBrowseDialog.
-At runtime click the browse button to open the "Browse For Folder" dialog and click the "Make New Folder", type a name for the newly created folder BUT DO NOT PRESS THE ENTER KEY and click the OK button, the Value is set to "New Folder" instead of the name I have typed.

1. Add a RadMaskedEditBox and a RadCheckbox to your form.
2. Add ToggleStateChanged event to the RadCheckbox.
3. Use the following code:
private void radCheckBox1_ToggleStateChanged(object sender, StateChangedEventArgs args)
{
    if (args.ToggleState == Telerik.WinControls.Enumerations.ToggleState.On)
    {
        radMaskedEditBox1.Mask = "^[0-9]{5}$";
        radMaskedEditBox1.MaskType = MaskType.Regex;
    }
 
    else if (args.ToggleState == Telerik.WinControls.Enumerations.ToggleState.Off)
    {
        radMaskedEditBox1.Mask = "";
        radMaskedEditBox1.MaskType = MaskType.None;
    }
}
4. Start the application
5. Check and uncheck the checkbox (now ToggleStateChanged event was fired)
6. Type some letters to the RadMaskedEditBox (e.g. "aaa")
7. Press tab

Workaround:
RegexMaskTextBoxProvider provider;
private void radCheckBox1_ToggleStateChanged(object sender, Telerik.WinControls.UI.StateChangedEventArgs args)
{
    if (args.ToggleState == Telerik.WinControls.Enumerations.ToggleState.On)
    {
        radMaskedEditBox1 = new RadMaskedEditBox();
        radMaskedEditBox1.Mask = "^[0-9]{5}$";
        radMaskedEditBox1.MaskType = MaskType.Regex;
        radMaskedEditBox1.MaskedEditBoxElement.TextBoxItem.HostedControl.Leave += HostedControl_Leave;
        provider = (RegexMaskTextBoxProvider) radMaskedEditBox1.MaskedEditBoxElement.Provider;
    }

    else if (args.ToggleState == Telerik.WinControls.Enumerations.ToggleState.Off)
    {
        radMaskedEditBox1.MaskedEditBoxElement.Mask = "";
        radMaskedEditBox1.MaskType = MaskType.None;
    }
}

private void HostedControl_Leave(object sender, EventArgs e)
{
    if (radMaskedEditBox1.MaskType == MaskType.None && provider != null)
    {
        provider.GetType().GetField("mask", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).SetValue(provider, "*");
    }
}

To reproduce:
- Set the mask like this:
private void RadForm1_Load(object sender, EventArgs e)
{
    radMaskedEditBox1.MaskType = MaskType.Regex;
    radMaskedEditBox1.Mask = "^[0-9]{6} [A-Z]{4} [0-9]{7}$|^[0-9]{5}$";
}
- Start the application, enter five digits and pres Tab.
- The error icon apperas.

Workaround:
- Set the Mask before the MaskType:
radMaskedEditBox1.Mask = "^[0-9]{6} [A-Z]{4} [0-9]{7}$|^[0-9]{5}$";
radMaskedEditBox1.MaskType = MaskType.Regex;

To reproduce:

public Form1()
{
    InitializeComponent();
    this.radMaskedEditBox1.Mask = "9999999999";
    this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Standard;
    this.radMaskedEditBox1.PromptChar = Convert.ToChar(" ");

}

private void radButton1_Click(object sender, EventArgs e)
{
    this.radMaskedEditBox1.Clear();
    this.radLabel1.Text = "Value = " + this.radMaskedEditBox1.Value + Environment.NewLine + "Text = " + this.radMaskedEditBox1.Text;
}

Workaround:  set the Value to null as well.

Currently, when Delete is pressed the min values is set, however, the textbox should be cleared. 

This can be handled by using a custom provider:
public class MyFreeFormDateTimeProvider : FreeFormDateTimeProvider
{
    public MyFreeFormDateTimeProvider(string mask, CultureInfo culture, RadMaskedEditBoxElement owner)
        : base(mask, culture, owner)
    { }
    public override void KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyValue != 46)
        {
            base.KeyDown(sender, e);
        }         
    }
}

To reproduce:
- Set the provider to FreeFormDateTimeProvider 
- Bind the control to a value.
- Clear the date and tab out of the control.

Workaround:
Seth the value in the ParsingDateTime event handler:

if (e.InputString == "")
{
    this.SetToNullValue();
}

To reproduce:
- Set the value to February 29.
- Open the drop down and zoom 3 times.

Workaround:
private void Calendar_ZoomChanging(object sender, CalendarZoomChangingEventArgs e)
{
    RadCalendar calendar = sender as RadCalendar;
    if (calendar.FocusedDate.Month == 2 && calendar.FocusedDate.Day == 29)
    {
        calendar.FocusedDate = new DateTime(calendar.FocusedDate.Year, calendar.FocusedDate.Month, calendar.FocusedDate.Day - 1);
    }
}

Workaround: 
((StackLayoutElement)this.radBrowseEditor1.BrowseElement.Children[2]).ShouldHandleMouseInput = false;
this.radBrowseEditor1.BrowseElement.TextBoxItem.RouteMessages = true;

To reproduce:

Place a MaskedTextBox on a Form
Set 'MaskType' to 'Numeric' (and in my case I have Mask set to 'D' to allow integer values only)
Run the application / open the form - by default the masked textbox has a value of '0'
Elsewhere (i.e. notepad) enter and copy a text like 'CT_1234' into the clipboard (please note the starting non-numeric string characters)
Go back to the application / form and click into the masked text box
Select the pre-existing value (by default  the '0' mentioned above or any other value i.e. '11111' .. and by select I mean via mouse or [Shift]+[Arrow Key Left/Right])
Press [Ctrl+V]
>> Nothing happens
.. what should happen though is that the selected text is overridden with '1234'
However, if you have no text selected in the masked text box and place the cursor in it i.e. at the very beginning or end of the existing value, pasting works as expected.. the value '1234' is added (and correctly 'dropping the 'CT_' in front of it).

To reproduce:
- Set the mask to numeric.
- Change the value and check the Modified property.

- Workaround:
string oldValue = string.Empty;

void radMaskedEditBox1_LostFocus(object sender, EventArgs e)
{
    if (oldValue != radMaskedEditBox1.Text)
    {
        radMaskedEditBox1.Modified = true;
    }
    else
    {
        radMaskedEditBox1.Modified = false;
    }

    oldValue = radMaskedEditBox1.Text;
}

To reproduce:

public Form1()
{
    InitializeComponent();
    this.radAutoCompleteBox1.AppendText("abc;");
}

Workaround: append the text in the Form.Load event.

private void Form1_Load(object sender, EventArgs e)
{
    this.radAutoCompleteBox1.AppendText("abc;");
}

To reproduce:

1. Please refer to the attached sample project.
2. Run the project and click the button. The two RadTextBox controls are left aligned.
3. Close the opened form and click the button again. You will notice that the RadTextBox is not left aligned.

Workaround: use RadTextBoxControl.

To reproduce:
 this.radDateTimePicker1.MaxDate = DateTime.Today;
private void radButton1_Click(object sender, EventArgs e)
{
    this.ValidateChildren();
}

Workaround:
this.radDateTimePicker1.MaxDate = new DateTime( DateTime.Today.Year,DateTime.Today.Month,DateTime.Today.Day, 23,59,59);

Workaround:
 radSpinEditor1.SpinElement.TextBoxItem.HostedControl.MouseWheel += HostedControl_MouseWheel;

To reproduce:

this.radSpellChecker1.AutoSpellCheckControl = this.radTextBoxControl1;
this.radTextBoxControl1.Text = "this is a test [doc]";

private void radButton1_Click(object sender, EventArgs e)
{
    radSpellChecker1.Check(radTextBoxControl1);
}

The "[doc]" is underlined as misspelled. However, if you click the button, no mistakes will be found.

Workaround:

char[] punctuation = " .,!?-\\/|~!@#$%^&*()[]_+=;:".ToCharArray();
TextBoxSpellChecker tbSpellChecker = this.radSpellChecker1.GetControlSpellChecker(typeof(RadTextBoxControl)) as TextBoxSpellChecker;

FieldInfo fi = typeof(TextBoxSpellChecker).GetField("punctuation",
    System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
fi.SetValue(tbSpellChecker, punctuation);

Note: When using WordByWord, the first suggested change is automatically shown in the "Change To" text box, however when using AllAtOnce, it is not, but the "Change" button is enabled. Pressing the Change button then adds the suggestion to the "Change To" text box, but doesn't update the word above, so you have to press the Change button a second time.

Workaround:

public Form1()
{
    InitializeComponent();
    this.radSpellChecker1.SpellCheckMode = Telerik.WinControls.UI.SpellCheckMode.AllAtOnce;
    this.radSpellChecker1.SpellingFormShowing += radSpellChecker1_SpellingFormShowing;
}

private void radSpellChecker1_SpellingFormShowing(object sender, Telerik.WinControls.UI.SpellingFormShowingEventArgs e)
{
    RadButton changeButton = e.SpellingForm.Controls["buttonChange"] as RadButton;
    changeButton.PerformClick();
}

Note: when you open the spell check dialog  and it iterates through the words, it does not highlight (select) the word in the linked RadTextBoxControl/RadTextBox, like it does in the Word's spell checker. 

Workaround: install .NET Framework 2.0 SP1