Bug#365128: Seen here also..
I have experienced exactly the same issue here, with a NVIDIA card.
Unfortunatly I don't have any log, I will try to get some.
But the strange bit for me was that I can still launch a new server via a
command line, it's only crashing with the "open new session" from kde system
Is it the same for you?
Took us away from civilization
Brought us to slave in this big plantation
Fussing and fighting, among ourselves
Nothing to achieve this way, it's worser than hell, I say