Hmm, that seems a bit short, I would never have set a timeout like that. Have you tried other browsers? Is anyone else having this problem? Typically timeouts are between 10-15 minutes, where I think vb default is 15. To be clear though, you are speaking about the forum timeout, not cometchat?
Cometchat though, I can't change that timeout unfortunately.
Also, how long are you referring to with a few minutes? How long did you expect a session to last? Too long and it can become a cpu load issue on the server.
It was set to 10 minutes, I just changed it to 15.