Eeerrrkkk, my desktop has gone :/

[Desmo]

Just to go one better than Del Lardo....my entire Ubuntu desktop has gone :/
I was adding a skydome to compiz settings when it went a bit funny. My four desktops dropped back to the normal two. I rebooted and now nothing loads up. No menu bars or desktop icons. I can still do stuff manually using Alt+F2 to run firefox, terminal, etc.

Trying to hunt down some info but no joy so far.