We're using the Q3 2011 release but haven't yet upgraded to the latest service pack, would this be likely to resolve the issue?
We don't get any error, VS/Blend simply crashes with a "Visual Studio has stopped working.." message. The control works fine when we add it via XMAL and build the application this way, the problem only occurs when we switch to design view.
We're also using other Teletrik controls such as TileView, DataGrid, DataForm..etc with no issues.
FYI, I remember reading that some people were experiencing crashes with Telerik controls and Visual SVN, we're currently Visual SVN 2.5.1 but then I suppose this wouldn't explain why it also crashes in Expression Blend?