Sorry for the inconvenience. You could try the following in order to delete the old ASP.NET AJAX VSExtensions and reinstall it:
1. Close all the instances of VS.
2. Delete Telerik ASP.NET AJAX VSExtensions and Telerik.CommonPackage directories from the following locations:
%localappdata%\Microsoft\VisualStudio\10.0\Extensions\Telerik ( or C:\Documents and Settings\[UserName]\Local Settings\Application Data\Microsoft\VisualStudio\10.0\Extensions\Telerik depending on your OS)
3. Open VS2010. Launch the Extension Manager, switch to the Online Gallery pane, search for Telerik and download and install the latest Telerik ASP.NET AJAX VSExtensions.
Please let me know if that helps.
All the best,
the Telerik team
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