Sorry for the inconvenience.
There is a rare case when some files remain from the previous installation and thus breaking the VSExtensions. I guess you might have experienced that exact problem. Could you please try the following steps in order to reinstall the Extensions?
- Close all Visual Studio instances
- Use Windows Explorer to check the following two folders for "Telerik WinForms VSExtensions" subfolders and delete them:
3. Open VS2010 and go to Tools -> Extension Manager. Go to the Online Gallery and in the Search field in the top right corner type Telerik.
4. Download and install Telerik WinForms VSExtensions. Restart the studio if it prompts to.
5. Try again to create new Telerik Project or to upgrade an existing project to the latest distibution.
Let me know if that helps.
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.