I tested the same approach using the 2011.1.419.1040 and I still were unable to detect any issues. Can you please make sure that the issue isn't caused by your custom implementation? You can compare our approach (implemented in the previously attached solution) with your real-life scenario implementation to see if there is something missing.
Also, please note that since Q3 2012 we officially do not support Silverlight 4 and we strongly encourage our customers to migrate their solutions to Silverlight 5 as soon as possible. This will give you the chance to work with our latest release and take advantage of the new and improved ribbon control - RadRibbonView
. Moreover, this will allow you to take full advantage of all new features and fixes implemented in our controls.
Pavel R. Pavlov
the Telerik team