Comment 18 for bug 178634

I've got the same model laptop, and I've been trying to solve this problem for over a year.
I've tried the fix, and it does in fact work. With up-to-date xorg ati drivers, I get great results.

I had previously filed a bug about this issue on the kernel bugzilla:
http://bugzilla.kernel.org/show_bug.cgi?id=8815

Thanks to the Ubuntu developers, and I hope that this fix gets pushed upstream!