Having problems logging in/out

This has been going on for a while, actually, but I'm finally annoyed enough to post about it here.

First off, I've been getting an error screen when logging in lately. Something about undefined heading length? I dunno. It doesn't do anything, and everything's fine if I refresh, it's just... a bit irritating sometimes.

The other thing is a bit more serious. Now and then, my account just... logs out. It usually happens when I log into the chat, or shortly thereafter. The only clue I get is that everything stops refreshing; if I go back to the main forum, it shows me that I'm logged out, and I can log back in and then everything works normally.

I'm not sure what the problem is. It's been like this ever since I got unbanned.