About your first question, VS2010 Designer supports only Panel
and their derivatives as the root element. Because of this, the message you have received is correct. Check this
link for more information.
error, I tried to reproduce it but without succeed. Could you please send us more information about your VS2010 version, Telerik RadControls installation package version and which regional settings you are using ? Also, have you installed a previous version of the Telerik RadControls ?
This will help us to clarify the problem. Thank you!
the Telerik team
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