Not staying logged in after server crash

[Melfra]

My host recently had a massive server snafu that I'm trying to recover from. The forum escaped relatively unscathed except for one problem: users can't seem to stay logged in. I'll be able to view topics, post, reply, etc. But when I try doing things such as editing theme stylesheets or changing someone's profile using the ultimate profile mod, the user either  a) is logged out or b) receives a message stating "The user whose profile you are trying to view does not exist." (Made a test account, seems that new users are able to start and edit ultimate profiles, but unable to edit stylesheets.) For what it's worth, the only information that seemed to have been affected in the crash was the database. Is there anything in there that could be causing this? I've been trying to look through the tables for something that might be causing this, but since I'm not super familiar with the database structure on smf, I haven't been able to find anything.

Running SMF 2.0.11
URL: http://www.turtle-paradise.net/forum/index.php [nofollow] (not sure if that helps, but one can hope!)

Thanks for your help! I'll be more than happy to answer any additional questions. Really hoping it's something silly I overlooked!