I tried to install Xmonad and use it on ubuntu 12.04 in VBox. Unfortunately it doesnt work and all I get now is black screen on reboot. How can I manually revert to Unity.
EDIT: solved by manually booting in safe mode and then removing Xmondad virus and manually changing default session. If you dont remove Xmonad you can manually change settings all day but parasitic Xmonad will change it back to xmonad.
Get a LiveCD disk, and boot from that. Note: You may have to change the order of the boot in the BIOS. Get rid of XMonad by the command line, or by the Ubuntu Software Center. (If you did it from there.) Then reboot.
When you get to the login screen, press the Ubuntu cog on the login box. (Sorry it's GNOME, but it will be the Ubuntu logo when you get there.)
It should come up with these options:
Now click on 'Ubuntu', or if your PC doesn't support Unity 3D then click 'Ubuntu 2D'. Login and hopefully you should have Unity back!
Hope this helps!