I cannot reproduce the behavior you have described, but what you can do is increase the margin of the main panel hosting the groups of the RadRibbonBar
which will allow you to see more of the white background. I have attached a screen shot to ease your way to the margin property you need to set.
I hope this will help you. If you need further assistance I would be happy to provide it.
the Telerik team
Q3’10 SP1 of RadControls for WinForms is available for download
; also available is the Q1'11 Roadmap
for Telerik Windows Forms controls.