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What should I do when Ubuntu freezes?
I updated Ubuntu 12.04 from 11.10 and in the begining I did not have any problem, but after some upgrades when I booted Ubuntu 12.04 from the grub it frozen in the starting screen (the UBUNTU word with the dots). I reinstalled 12.04 many times from the LiveCD and after some upgrades it happens the same including the message (before the starting screen) that the intel graphycs acceleration failed