Paint Event - Fired but no display update

Has anyone run into this problem I have a couple of panels in a Windows Form. I created paint event functions for the two panels for the purpose of drawing a diagonal gradient across my form. This works really well on my laptop. However, when I copy the solution to my desktop computer, the display doesn't get updated. According to my breakpoints, the paint events for the two panels are getting called, but the screen doesn't update. This code ran fine on my desktop two weeks ago before I copied it to my laptop. I have other forms that have panels that do their own drawing and they all exhibit the same behavior. I'm assuming that this is a bug, but I don't know where it came from or how to track it down. Any ideas

Bob