Originally posted by entropy_kid
then the NVidia screen comes up and I am at the KDE login screen.
That would be your X server dying. When that happens, the best place to look for a reason would be the X log file -- unfortunately, in your case, you have X set to respawn itself immediately, which immediately deletes the relevant log file and starts up another one.
Boot to runlevel 3, which is text mode login, and then do a startx
to get into KDE (if KDE isn't the default, then doing an echo exec startkde >~/.xinitrc
should fix that). Then, work on reproducing the crash, and once it happens (I know, it might take a while), copy the /var/log/XFree86.0.log file to somewhere else (like your home directory). Then startx again, and attach the file to your next post.