I'm sorry you are running into this problem.
I was not able to reproduce it using our latest official SP1 release(2011.2.1117) as you can see from this video:
If you haven't done so already, please upgrade to this release. You can download it from your Telerik account here: Public URL
If you still have this problem after the upgrade, please send as a sample WPF project that exhibits the same behavior, so we can reproduce the problem and fix it.
the Telerik team
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