Hi, i am much a newbie myself and probably this may seem dumb, but, here it goes anyway:
When you press Ctrl+Alt+F1 you go to the linux command line, what do you mean with Xserver crashes??
did you try pressing Ctrl+Alt+F7 to get back to X11?
I donīt know much about KPPP, but look in configure-->misc --> maybe you have enable "disconect when X server shoutdown" or something like that
Well hope it helps, if not well, good luck!