This is an update on this issue. The "slowness" is not caused by the server we are on (content loads fast and in full), but on the glitch in the vBulletin code. Actually I shouldn't bash vBulletin as its a good product. Rather my head is to blame. I can honestly say it was my mistake and I should have never done it, but my curious monkey hands are always looking for trouble!
While performing minor changes in the layout I have taken away one of the forum hacks we had previously had installed, and the problem started to appear right after the change. Of course, being me, I didn't think of saving a copy of the original code so we are all stuck with this. However, the good news is that it is not going to go for long as we are working to rectify the issue.
I sincerely apologize for the inconvenience and emotional pain
caused to each and every one of you. I am happily banning myself from performing any code changes again.