Hello Walther Siksma,
Thank you for writing.
We are sorry to say that there are some glitches with the RadRibbonForm under Vista, which we are working on fixing for the next release. Currently, you could try using our ShapedForm with RadRibbonBar docked in it, however this is only a workaround until we fix the ribbonForm. What form are you currently using?
the Telerik team
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