If you're getting a lot of segmentation faults, it may be more than the WMs... KDE and Gnome should not affect each other, since only one should be running at any given time.
I have had a serious problem in the past with random jobs seg-faulting that was caused by faulty memory. I wasn't affected that much by using the command line (lynx, slrn, mail, etc...), but opening X would use a sufficient amount of my memory to hit the dodgy chip...

How old is this machine?