Comment 59 for bug 407040

This is still present in Karmic RC. Note that this bug is different from the 'DMA failed to stop' error.

The differentiation is whether you are able to remove and reinsert the module.

If you do:

sudo rmmod ath9k
sudo modprobe ath9k

and you get

[ 900.135286] ath9k: Couldn't reset chip
[ 900.135298] ath9k: Unable to attach hardware; HAL status -5
[ 900.135449] ath9k 0000:06:00.0: PCI INT A disabled

in the dmesg output then you have this bug

If the wireless restarts correctly you probably have this bug

https://bugs.edge.launchpad.net/ubuntu/+source/linux/+bug/460886

Note that you may have both...