Second thing, I had mem problems back in May, and the fix was to su; 
   sleep 60 < /dev/mem; ^d back to your user, and then "startx".  Your
   "checkDevMem" reminded me of that, but I'm not sure if this is the
   same cause of your problems.

That was due to a short-lived bug in /dev/mem.  It's been fixed for a
long time.