Video Freeze

[Chris]

I experienced a video freeze this afternoon running 14.04.4 LTS with the
kernel shown in my sig. Some trace information was inserted into my
syslog which I've put up on Pastebin and can be downloaded here -
https://pastebin.com/d2Kp7vQ3 can anyone tell me what this might mean
and is it related to a video freeze in which the clock is frozen, the
mouse cursor will move but I can't switch between desktops however all
background processes, fetchmail, procmail, Spamassassin and others
continue to run.

Thanks
Chris

-- 
Chris
KeyID 0xE372A7DA98E6705C
31.11°N 97.89°W (Elev. 1092 ft)
15:19:18 up 2:12, 1 user, load average: 0.81, 0.64, 0.56
Ubuntu 14.04.4 LTS, kernel 4.4.0-24-generic #43~14.04.1-Ubuntu SMP Thu
Jun 9 09:46:12 UTC 2016