I figured out what the problem was...
My website could be accessed by either typing in "domain.com" or "www.domain.com"...
Which I found out is not good for a member's site because.....
When logging into the members section of the site, if I logged in to just "domain.com", and then went to "domain.com/forum", it would work fine. The cookie would work and I could use the forum as that logged in member. But if I logged into "domain.com" and then went to "www.domain.com/forum", it wouldn't recognize me as logged into the forum. So I realized that the domain name has to either be with or without www on all pages.
So the workaround I found for this, which I'm glad this happened so I now I know, is to create an htaccess file that does a 301 redirect to automatically resolve the domain name to "www.domain.com", so if any user tries to put in domain.com it automatically goes to www.domain.com. Which also is more useful for search engine optimization. So traffic stats aren't split up.
So what was happening to me was when I tried the forum at home on IE, Nav and Safari, I was always using just domain.com for my resolution and therefore everything looked good. But at the office, I ended up logging in to www.domain.com url but then going to domain.com/forum and so I thought the programming was messed up but it was just the url issue.
Hope that is clear enough and explaination, incase anyone has this problem in the future.
BTW, I LOVE MINIBB, IT'S EXACTLY WHAT I HAVE BEEN LOOKING FOR.