I updated f16 a few days ago after postponing updates for about 3-4 weeks. There were about 600MB of upates. After I finished, I discovered that the first login always fails. It tries to launch even before I hit return after entering the password, and then the login screen pops up again. I also cannot swich user at all (have to restart).
I thought it must be a bug and figured it might be fixed soon, so I waited a few days and tried another update. Not only did this not fix the problem, but now the network icon is missing and I have no access to wireless settings (a box states no network is available, though the wifi network in fact is connecting).
I tried using grub to load a 2-earlier version of the kernal, but the problems remain. I also tried a history rollback using yum, but some packages failed to roll back and again, the problems remain.
I'd be interested in some ideas.
I also tried reinstalling bash as suggested in sticky note above, but that didn't work. Also reinstalled kernal 3.3.7 with no change.