<< I still couln't figure this out...it has to do with checking your mail or something? I find this a lot in the sale/trade forum >>
You notice how every time you go to the forums it's a different list of messages?
Basically the ones at the top are the messages with the newest replies. When someone replies to any message at all in that forum, the message goes to page 1 at the top of the list. Every other message gets dropped down 1 notch. When someone "bumps" a message they are sending it to the top of page one, basically bumping it back into the space that people look for messages.