Restoring LG Optimus 2X P990 back to stock LG software
There is a zip file that is posted in this video description that you can flash via Clockworkmod or your favorite custom recovery that will revert your device completely to stock (including removing the recovery image and such).

The video goes through the process step-by-step, for your convenience, but it's basically flashing that file via CWM, and then being happy :)

It also goes through how to unroot, if needed!