Having successfully installed Ubuntu 11.04 I decided to look into improving look and feel of the unity desktop. I could find no option to introduce any nice effects with the standard install, but a google session suggested Compiz would do the job. I installed this and selected the "Wobbly windows" option and this worked fine.

After a while I thought I'd try some of the other available effects (can't remember which but may have been cube desktop) but this resulted in no windows showing at all. I now have just blank wall paper with no icons or menus. There are no error messages and right clicking the desktop produces a small context menu but nothing else. Rebooting brings me back to a blank desktop with just wallpaper.

I do not know where to start.