While agree that this question is a possible duplicate of the Reset question, I do have a solution.
- Log into the recovery console.
unity & gconf-editor & unity.*
- In gconf-editor, navigate to
- Double click the value "active_plugins".
- Remove the cube from the list.
- Close gconf-editor and the terminal window (to logout).
- Now when you try to log into unity it should work. If it does not, you can try from the first step again, and see if unity gives you any useful errors, leading you to the plugin you need to disable.
* This will start Unity (thus loading that compiz profile just in case), which will fail of course, but then launch the gconf-editor and metacity. It can also give you useful output when unity fails to start.