yeah, I did that Cez, long ago.
I'm a web developer (mostly Flash and Wordpress), but I've used this forum software before (back in '05), and I know you can set the amount of time before a user is logged out due to inactivity.
The idea is to log people out to lighten the burden on the servers (if people aren't doing anything, you log them out to allocate more server processing power to those who are actually doing something on the site), BUT HF has it set too low I believe!!
Add this to a long list of web developer/designer gripes I have about this site. Step it up or pay me to

, I got layed off!