nvidea drivers? if your X has a lockup, it could be because of an driver problem.
there is one big problem with the drivers of nvidea; they are binary only. Because the kernel is constantly in development, the drivers get broken now and then. ..imho the Windows-way simply doesn't apply to Linux, because of the active kernel development, but I believe they don't share this idea... (and off course, there are other reasons to hide your source)
Try to re-configure /etc/X11/XF86Config, either by hand, or with some tool. does nvidea also provide such tool?
if your X ever gets a lockup; don't pull the plug yet! If your keyboard lights aren't flashing, your kernel is still working, and all other programs are still running too! In fact, you could login remotely (ssh, and putty for windows), and close all other programs, and even try to kill your X server..
(but this might not work though). you could also type "reboot", to reboot your machine
commands like 'top' 'ps auxf', 'kill' and 'kill -9' are your friends
ps. your machine has a reset button; use it instead of pulling the plug