I find alot of forum software these days does that kind of stuff. I've found the only way I can usually make it work is to log in and tick the 'permanent log in' box. Everytime I clean all the cookies, cache, etc. and need to log back in, it's a real pain in lots of forums.

I'm also finding that very often, the software won't let you submit a post without previewing it. That's a waste of time!