Just want to make this public:

I had the problem that the GridView would not save any changes made in the Property Builder or whereever I do the changes.
After consulting with Telerik Support we found that you have to run the VS2008 as Administrator and it works well then.

Thanks Support Team.

Hi Ralf,

Thank you for sharing this very useful information with the community. I have updated your Telerik points for your post. We are current working on this issue and hopefully we will be able to fix it in Q1 2009.

Best wishes,
Nick
the Telerik team