So you are using the March 2 Nvidia drivers?
I did not see that behavior in Vista, but I seem to remember certain types of applications can cause the aero glass to stop working. I was running a 6800 though. Is it all of the Nero Applications that cause it?
One thing you might check, is Nero has a problem with the DPI setting if it is not default 96 DPI. You might check and make sure yours is set that way. Your problem has not been been caused by this setting as far as I know, but you might check anyway.
Do you have the Burn gadget in the Sidebar? Just asking in case it might be relevant.
You don't have it set to run in some compatibility mode, do you?