This is what I do in order for this problem to occur.
1. After signing in on my user account, i click log off.
2. I select switch use
3. I log in using the only other accoun
4. I click on the log off button and click switch users on the current accoun
5. I switch to the 1st account I was talking about, then all the sudden the wallpaper gets removed and a solid blue wallpaper goes in place of it.
Maybe this could have something to do with stylexp, a Windows XP theme program. I hope the xptheme.dll that it changed isn't causing this problem. Someone please help. Thanks.