GConf Cleaner is a tool to clean up the unknown/invalid gconf keys that still sitting down on your gconf database.
saves a heck of a time having to re-install mint everytime we get an error or a program suddenly stops functioning.
note that still on early stages, but seems to work, worth a try before reinstalling mint.
It's still in early beta, needs some further tunning. For some weird reason it deleted my workrave personal settings files (not a big deal), may have to report the bug. Anyway this one is one to watch since a lot of programs seem to break or stop functioning completely in mint/ubuntu for no reason.