This is a known issue and it will be addressed in an internal build in the first week of January 2010. For the time being, you can use the internal build that we released shortly after the official Q3 2009. This release is the latest version that does not have the described issue.
You can find the internal build (for customers) at Your Account >> Downloads >> RadControls for WinForms >> Older Versions >> 2009.3.1103 >> Latest Internal Builds.
For our trial users the path is: Your Account >> Free Trials >> RadControls for WinForms >> Older Versions >> Latest Internal Trial Builds.
If you have additional questions, feel free to contact me.
the Telerik team