I have the following problem:
My Wifi works without problems under kernel 2.6.28-11 but it fails under kernel 2.6.28-13. I’m using the ath_pci driver.
Apparently there has been a change in the ath_pci wifi driver in kernel 2.6.28-13 that my hardware do not agree with.
Some people reports that the ath5k driver should be working but I can’t make it work on my machine.
By the way – I’m using Wicd as my wireless network manager without problems under kernel 2.6.28-11 in Gnome and KDE.
My advice for the moment is to stick with the 2.6.28-11 kernel to avoid wifi problems.
See also this link at Ubuntu forums