We have a very strange registry issue, it only seems to affect one registry key.

We currently utilise a custom logon screen image on both Windows XP and Windows 7. The logon screen on Windows XP for example has the standard windows XP theme although from time to time we will stumble across a machine that suddenly has a classic windows XP theme on the logon screen and the wallpaper registry key is blank so our lovely image is missing.

I can't understand what causes this as none of our users have access to change the registry, we have also noticed it on Windows 7 on one occasion that the OEMBackground key resets itself from 1 to 0.

Has anyone had this before?

Cheers for any help!