Comment 12 for bug 129719

I built the rt2x00 git kernel tree, and used that in combination with network manager. With that combination, suspend/resume works without this unregister_netdev trouble.

You can easily check by issueing the command:
/usr/bin/dbus-send --system --dest=org.freedesktop.NetworkManager --type=method_call \ /org/freedesktop/NetworkManager org.freedesktop.NetworkManager.sleep

followed by
sudo pccardctl eject

this last call locks up the ubuntu kernel with the unregister_netdev problem, while the rt2x00 git kernel does not. I guess the driver has changed quite a bit since (as the rt2x00 developers are very active again) the snapshot in the gutsy kernel. I suggest re-sync'ing with the git tree (but the latest git is not API compatible with the gutsy kernel)

(this problem only arises with the pci/pcmcia version of course)