Comment 56 for bug 750437

Same problem here with Ubuntu 12.04 with latest updates and a Radeon HD3600:

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV635 [Radeon HD 3650/3750/4570/4580]

Tried the nomodeset trick mentioned above but it did not solve the issue.

The problem occurs both with the open source driver and fglrx.

Installing manually fglrx legacy drivers from AMD site seems to reduce the freezes but it still hangs with the firegl_sig_notifier crash from time to time.

If I first logout and then shutdown it seems to avoid the freeze (similar to the trick above of killing xorg before shutting donw).