Comment 25 for bug 1027380

Well, that is a RC1.

So as the above bug wasn't introduced until the RC7 kernel, the fact that the RC1 is not effected is not surprising.

Can you try with a post RC7 build? i.e. such as the daily build in the link I posted earlier.

That is the most recent mainline build, in which the bug from the RC7 it is supposedly fixed.

If that works OK, then when the kernel team rebase to the next RC8 and upload ubuntu kernel based on that the problem should resolve itself without anyone having to do anything more.