We were getting Unhandled SEHException that we could not figure out. We were getting these from calls inside combobox.SelectionChangeCommitted.
We stumbled on something in a Google search that pointed us to EnableVisualbeStyles. We found an even better link after digging into this more:
http://pluralsight.com/blogs/craig/archive/2004/08/22/1998.aspx
We got rid of the call to EnableVisualStyles and added a Manifest file and we are now bug free.