So further to my post about roaming profiles going screwy i.e.
When a roaming user logs off their profile isnt fully deleted meaning when they log on they get a second profile on the computer called Username.Domain.
This second profile results in a black background because the following registry key: HKEY\Current User\Control\Desktop\Wallpaper\ points at their orgininal profile which is half deleted.
To fix this you need to ensure the profile is deleted so I’d recommend a policy to turn off the PC’s off in the evening with a shutdown script to run Delprof2.exe. If this still doesnt work then you can cheat a little and change the registry to point at the roaming profile:
Key: HKEY\Current User\Control\Desktop\Wallpaper\
Although if your sensible you would have a mandory wallpaper and wouldnt have this issue (we’re not as users like pictures of their kids).