Comment 93 for bug 33617

I made another experience which could give more clues (I kept the same xorg.conf file and always without battery installed):

1- shutdown, unplugged everything for 1 minute, plugged the AC
2- powered it on, xorg desktop boots fine, glxgears during 30 minutes and other 3D apps without lock
3- safely reboot via KDE
4- xorg desktop boots fine again, run glxgears during 30 minutes and other 3D apps without lock
5- safely shutdown via KDE for 1 minute
6- powered it on, xorg is only a black screen, hear start-up sound
7- pressing the laptop power button to safely shutdown, the laptop shutdown completely by itself
8- let the laptop cool for about 1 hour but WITH AC adaptor still CONNECTED!
9- all laptop seems at the room temperature
10- powered it on, strange, xorg desktop boots fine and run glxgears without lock
11- safely shutdown via KDE for 10 minutes
12- powered it on, xorg is only a black screen, hear start-up sound, seems not freezing

With this experience, we could think that there is an overheating problem or some persistence in a chipset memory (AGP, BIOS, video...) that is "cleaned" with time or with complete power down. Maybe I am completely wrong... or maybe not.