My system runs pretty well providing I don't leave it unattended. Every time I leave it untouched for 10 mins or so it just freezes completely (100% repeatable). No mouse, no keyboard, no disk activity, not a sausage. Screen is left just as it was (ie: you don't know it's crashed until you try to type or move the mouse). Reboot is the only solution.
So far I have disabled all power and screen saving. There are no core dumps that I can see and nothing in any log. Interrupts / dma settings look OK to my untutored eye, everything to do with screen settings (fglrx driver) looks normal so I guess X is happy. My hardware is fine (works faultlessly with Fedora).
Any suggestions where to look next please?
UPDATE: Leaving system idle but displaying a virtual terminal stops the freezing. (Can then return to KDE with CTRL-ALT-F7 OK) Terminal prints this message:
after being idle for several minutes.[ 5035.852402] INFO: rcu_sched detected stalls on CPUs/tasks: { 0} (detected by 2, t=15498 jiffies)
[ 5035.852614] INFO: Stall ended before state dump start
