Well about week and a half ago I gota virus that hijacked the wallpaper and made it a fake error background. That virus is now removed but starting yesterday I started to have this happen. Now the only way to change the background is to open a picture in firefox and use set as desktop background.
looks like the virus left its trace... maybe do a repair install? should fix it. repair install will not touch your files, it only overwrites your system files.
