Re: Blank screen after exit X
known bug with 177+ drivers which will cause x to lock up to 100% cpu upon restart (which kdm/gdm do after logout). Nvidia just barely acknowledged this problem a few days ago despite the months its been affecting people so who knows when they'll fix it. On the bright side (yea right) if you change your gdm/kdm timeout to be something like a minute or two it'll start up just fine minus that minute or two with 100% cpu xorg. Also, you can recover your console by just starting X by hand (e.g. X from console) and waiting a minute or two for it to start.
There's a thread on this somewhere around on these forums...