[ubuntu] Ubuntu 12.10 freeze

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http://ubuntuforums.org – I installed 12.10 from USB. the system always completely halts within 3 minutes (no idea what triggers such behaviour, but I suspect problems with graphics). I managed to install Gnome Shell and on that platform I can work smoothly. but if I try to switch back to Unity I still get that freeze. Running 12.10 Unity from DVD or USB gives no such problems. Any ideas? I really dislike Shell UI.... Thanx in advance (Hardware)