Hi.
Maybe too late but at least a solution.
Today I had the same problem with a Acer Aspire 5250-0619 (64bits) laptop and using 12.1 GNOME.
Thanks to https://bugs.launchpad.net/ubuntu/+source/linux/+bug/989566 I could fix it, except that instead of issueing the command I re-booted the laptop and that was it.
It works like a charm.
Luis.