Rundll32 has stopped working error on Vista

I've seen this problem on two different systems. Both were HP laptops running vista. Some brief time after logon the error comes up the Rundll32 has stopped working. Looking in the event logs I see that the associated module is User32.dll (in both cases). I think I may have found the problem. At least this system to work. I had installed Nvidia drivers for the video from the Nvidia website. This installs a Nvidia Driver Helper Service. I think this service had something to do with the problem. What I ended up doing was uninstalling the Nvidia video drivers through the control panel. Rebooting. Then right clicking my computer, choosing properties, clicking Device Manager, expanding Display, right clicking the standard VGA and choosing update driver (and having it automatically do it from the web). It installs the drivers without the helper service. After doing this, the rundll32 has stopped working errors went away.