Desktop Icons And Taskbar Revert Mysteriously To Previous Arrangement

Using x64 Ultimate SP1 here. Just tidying up my desktop and taskbar to the way I like them. Nothing too tricky here, just minimizing clutter and placing shortcuts to Adobe CS5 apps on the task bar after upgrading from CS4 to CS5. My prior desktop was a bit more cluttered with shortcuts, and the taskbar held only CS4 shortcuts pinned to the bar. After setting everything to the way I want it, saving my desktop theme, and even rebooting a few times, the desktop configuration seems static. I also created a restore point with the new desktop and taskbar arrangement included.

But, come back the next day and it's all back to the old cluttered desktop and CS4 icons pinned to the taskbar! It doesn't seem to affect my desktop wallpaper settings, though --only the dtop icons and pinned taskbar icons. Not using any 3rd party desktop managers or the like. It always seems to happen sometime during the night. When I check to see whether a Windows update has taken place, most times there hasn't been one. This has been going on now for over a week. Sure getting tired of the system restore routine just to get back to my current desktop config.