Make sure that you are using the "recommended" drivers.
Make a new launcher on the desktop or in the desktop folder
in the command section "gksudo mintinstall" call it Software Manager, and BAM.
I noticed that it never asked me for my password on the KDE and it asks for it in the regular distribution it did ask for the password every time it started.
KDE is pretty finicky and mintinstall needs root privileges or it crashes out with 'Segmentation fault'
which made me check drivers and what not; and then it hit me, it needs to be root.
Sometimes it stays running sometimes it doesn't.
Also if you want a complete fix, use the real version of java, openjdk and python have some issues working together. Remove openjdk and use sun java jdk, reboot and everything should be copacetic. I sat down and tried to fix the code and only broke it further and realized that real java worked better. I know it is a little late in the game with mint 13 around the corner and mint 13 KDE being released soon after, but it does work for now, and for those like me choosing to stay on mint 12 due to xorg issues, this should get you through until the next version of xorg with the nvidia fixes.