Fixed an MTRR issue that CONFIG_MTRR_SANITIZER was not able to correct (ftp://ftp.cs.utoronto.ca/pub/hugh/
), upgraded to Xserver 1.9.4 (from 1.7.7) and 270.26 but still getting X hangs here, this one caused some messages about recovering a GPU error, which is also displayed in nvidia-settings (count: 1, so far).
EDIT: upgraded from 188.8.131.52 to 2.6.37 also.
[209779.760] (II) NVIDIA(0): The NVIDIA X driver has encountered an error; attempting to
[209779.760] (II) NVIDIA(0): recover...
[209779.770] (II) NVIDIA(0): Error recovery was successful.
[209805.710] (II) Open ACPI successful (/var/run/acpid.socket)
[209805.764] (II) NVIDIA(0): Setting mode "nvidia-auto-select"