I was previously using ubuntu version 12.10 and I recently upgraded to version 13.04. Everything was working fine until I updated. Immediately after the update, my wallpaper cannot seen on screen again. Also when I use darker themes such as dorian themes, my desktop freezes. I tried all the suggested helps and answers such as dconf editor but there is no way forward.
Searching the web for answers reveals that this appears to be a general problem. I really need help.