Cannot evaluate expression because the current thread is in a stack overflow state

Hi everyone

I am using Crystal Reports with Visual Studio 2010 and have the following problem:

When I create a group name field and start the program, generate the report everything works. Shows the grouping on the program. But if  in the left hand panel with the tree drop down I click on one of the names of the group, everything stops and the app crashes and I get an error

"Value cannot be null" (null exception)

On show detail I get the

Cannot evaluate expression because the current thread is in a stack overflow state.

Without grouping everything works but that left sided panel is empty so there is nothing to click inside, there is a possibility it would crash if there was.

Even if I click on the text Preview, it crashes, so without clicking on the tree it crashes. Any text in the group tree side panel and it all breaks down.

Any idea why this is happening?