I'm just posting a solution an error I was getting in Visual Studio 2010 as I couldn't seem to find a solution in the Telerik forums when searching. Forgive me if it's already posted.
When in Design mode all of my telerik controls on the page were showing the error "Error Creating Control - <ControlName> Object reference not set to an instance of an object"
I googled this error and found the 'workaround' solution at this link here
You basically have to go to the OnInit event of your page (or of the class your page is inheriting from) and surround your init code with a check to see if it's not in DesignMode. Once you have surrounded your code with this check, you must close your pages and rebuild the project to make it work.
here's the code example:
protected override void OnInit(EventArgs e)
This is a bug with Visual Studio 2010 and not Telerik.
Hope this helps someone.