Comment 13 for bug 424503

Got the same problem. The workaround described above solved the problem.
Output of lspci:
01:00.0 VGA compatible controller [0300]: ATI Technologies Inc Radeon Mobility M6 LY [1002:4c59]
 Subsystem: IBM Device [1014:052f]
 Flags: bus master, stepping, fast Back2Back, 66MHz, medium devsel, latency 66, IRQ 11
 Memory at e0000000 (32-bit, prefetchable) [size=128M]
 I/O ports at 2000 [size=256]
 Memory at c0100000 (32-bit, non-prefetchable) [size=64K]
 [virtual] Expansion ROM at c0120000 [disabled] [size=128K]
 Capabilities: <access denied>
 Kernel modules: radeon, radeonfb