Created attachment 723580 [details]
xdm.errors
One interesting line in the xdm.errors file is:
intel_do_flush_locked failed: Input/output error
XIO: fatal IO error 11 (Resource temporarily unavailable) on X server ":0"
after 260 requests (257 known processed) with 0 events remaining.
Which might lead one to thing that it's an intel chipset problem.