We recently updated all our Ubuntu machines from Edgy to Feisty. Updating went smooth, apart from a few problems.
The first problem was that X was freezing at random intervals. Xorg log mentioned nothing special, but the GDM log did:
Error in I830WaitLpRing(), now is 7023360, start is 7021359 pgetbl_ctl: 0x3ffc0001 pgetbl_err: 0x0 ipeir: 0 iphdr: 1810000 LP ring tail: 9b38 head: 938c len: 1f801 start 0 eir: 0 esr: 0 emr: ffff instdone: ffc0 instpm: 0 memmode: 306 instps: f0000 hwstam: ffff ier: 0 imr: ffff iir: 0 space: 129100 wanted 131064
Fatal server error: lockup
So I did the only thing I could think of: I removed the Videoram lines from xorg.conf. And the freezes seem to have stopped.