Work around: 
 void radRibbonBar1_CommandTabSelecting(object sender, Telerik.WinControls.UI.CommandTabSelectingEventArgs args)
        {
            if (args.NewCommandTab.Visibility == Telerik.WinControls.ElementVisibility.Collapsed || args.NewCommandTab.Visibility == Telerik.WinControls.ElementVisibility.Hidden)
            {
                args.Cancel = true;
            }
        }

It will be nice if RadRibbonBar has the QuickAccessToolbar property exposed in the property grid of Visual Studio, just like ExpandButton, ExitButton, etc.

The keytips not activating after splash form is closed and alt key is pressed. For the keytips of RadRibbonBar to break, the splash form (or any other form that appears before the form containing RadRibbonBar) should contain a RadControl. The workaround is to unregister the shortcuts that the RadControl in the splash form has. For example: ChordMessageFilter.UnregisterChordsConsumer(this.radTitleBar1.Behavior.Shortcuts); This line assumes that there is a RadTitleBar on the splash form.

The text of the quick access buttons looks doubled when an Office2010 theme is applied, and the Aero mode is turned on.
Update: This could be worked around with TextRenderingHint, BUT the font will not look ok when the mode of the form/titlebar is not Aero

1. Create a new project and open design time.
2. Add new RadRibbonBar instance.
3. Add some tabs and in one of the tabs add some groups.
4. Select the last added group and try to drag it. Exception will occur.

The property is not serializable, thus the items are not added.

The order of the tabs under the 'Edit CommandTabs' dialog is wrong after deleting all the contextual tabs.

Attempt to assign two RadButtonElements in RadRibbonBar the same Name at design time results with an Exception dialog instead of the standard dialog.

Setting the AutoSize property of RadRibbonBarGroup to false and resizing the group at design-time crashes VS.

If you set the MaximizeBox and MinimizeBox properties to false in RadRibbonForm with AllowAero = true, the maximize and minimize buttons will still appear.

When the AllowAero property of RadRibbonForm is true, the ContextualTabGroups placed on the ribbon bar do not support  HTML-like text formatting.

In some cases when the ribbon is collapsed and you click on a tab item to display its content in a popup, there is an improper top offset of the content.

To reproduce
1. Add a form with ribbon
2. Add one tab
3. Go to Code View
4. Go back to design time and add a group and a button in the group
5. Close design time and reopen it => the items are missing

To reproduce:
1. set a local setting to the back color of a ribbon tab
2. run the project and change the selected tab => your setting is removed

RadRibbonBarBackStageView positioning should be changed, so that the control appears 2 px lower.

When the Windows taskbar is in auto-hide mode and you maximize a RadRibbonForm, you cannot hover the taskbar to bring it to the screen again.

The Click event of the ExitButton and OptionButton is fired twice. If you subscribe to the ButtonElement of the ExitButton and OptionButton (which are RadMenuButtonItems), then you will get the click event fired just once.

FIX. RadRibbonBar - the Click event of the OptionsButton is fired twice

RadRibbonBarGroup consists of two FillPrimitives (in addition to the main FillPrimitive). These fills should be exposed to the user, so that s\he can tell what their colors should be.

Resolution: 
RadRibbonBarGroup consists of two FillPrimitives which are exposed: GroupFill and BodyFill. You can set their color using the following code snippet: 
radRibbonBarGroup1.BodyFill.BackColor = Color.MediumPurple;
radRibbonBarGroup1.GroupFill.BackColor = Color.MediumSeaGreen;

The button that opens the BackstageView is not correctly placed when the ribbon is placed on a RadRibbonForm with aero turned on.