Comment # 8 on bug 1085048 from Max Staudt

Thank you for the testing, Petr!

It shouldn't be boot related. Most likely it's a change in the kernel driver
that came with the newer kernels. There's also a smaller probability that
something changed on the X driver side, but that end is fairly peaceful these
days, since most code related to your problem has long moved into the kernel.

In fact, you could try installing an old kernel in your system. If things work
as before, then you know your culprit, and can point the upstream folks in the
right direction. Plus, it's VERY, VERY helpful to know which kernel works and
which doesn't.