Comment 45 for bug 347587

It is UXA specific and that is not the supported render method in jaunty. x-updates is for actual releases, forcing everyone using it to only have the UXA acceleration method by putting a 2.8 RC release on there where EXA is dropped is not a very good idea in my opinion. Not to mention the intel driver is only 1/3rd of the equation when it comes to UXA stability. You can install bleeding edge stuff by upgrading to karmic where the userspace can support it or alternately have a subset of karmic by using the xorg-edgers jaunty packages. 2.7.2 will probably be released around the same time 2.8 is and could potentially include this fix.

https://launchpad.net/~xorg-edgers/+archive/ppa