Camaleon -- OK, I've posted a concatenation of the last 3 Xorg log files to http://pastebin.com/eXhSQyEL . I'm pretty sure that the last one of the 3 (Xorg.20.log) was the one which was in use at the time of the problem, the next-most-recent (Xorg.0.log.old) was the one which started at that time, and the most recent one (Xorg.0.log) is from a restart performed this morning.
Thanks for all your help with this! -PT
