Comment 3 for bug 773018

Ok. Sounds like the same bug(s) I have, stemming from power saving attempts. There are two choices to fix that:

a)
The more conservative choice is to keep your supported ubuntu kernel and just disable those power saving measures.
You can do so by creating an empty file in /etc/pm/power.d/ with the name of those power saving scripts and without the executable bit set (see man pm-powersave):

sudo touch /etc/pm/power.d/wireless
sudo touch /etc/pm/power.d/pcie_aspm

Just the wireless part may be sufficient for you. The pcie_aspm issue is _very_ dependent on the details of the hardware. For me the wireless will stop working after a suspend/resume cycle if I go to battery then.

b)
You could also run a 2.6.39 mainline kernel if you do not need anything that only the ubuntu kernel has. Currently the newest ones available pre-compiled are:
for 64 bit: http://kernel.ubuntu.com/~kernel-ppa/mainline/v2.6.39-rc5-oneiric/
or for 32 bit:
http://kernel.ubuntu.com/~kernel-ppa/mainline/daily/2011-04-19-natty/
They are not final and not "supported". The kernels of choice for curious people like me :) . All data not backed up is disposable - but then it always is.