The problem most likely is a mix of several things, a forum this size doesn't need a load balancer, it just needs updating.
1) Using ancient vb3 software. It might work now, but it wont always.
2) Using an ancient PHP version, they're running 5.2.10, which is 4 YEARS out of date.
3) Probably using a MySQL version just as old.
4) Using apache, again, probably just as old.
Fixes are simple... realy...
1) Should upgrade to modern forum software such as XenForo, which, some of the largest forums in the world now run. It's based on modern, up-to-date coding practises, utilising many features and optimisations that vb3 cannot.
2) Update to php 5.4.x, possibly even 5.x
3) Update MySQL to 5.5, or, if running an InnoDB-based forum, then Percona server.
4) Switch to a high speed web server such as LiteSpeed or Nginx.