I just switched to VS 2010, and upgraded a previous project. I'm getting the following error on a page in design mode for 2 controls:

Error Creating Control - ObjectName 
Object reference not set to an instance of an object.

One of them is a simple label, and the other is a ajax update panel. Other pages look fine. When I build and test the app, the page renders fine in the browser and functions fine - the label functions as expected and the content in the update panel works as expected.

Any ideas why I'm getting this error? I tried some of the google results to no avail. It'd be great to get this out of the way.

Thanks!