Might aswell throw it out there.
May I request a change to the phpbb forum software?
It has a lot more features, and is a lot easier to use than vbulletin. And on top of that, is free.
A main problem I have with vbulletin forums, is that if I load the forum, then step away for 15 minutes, then come back, and refresh the page, all the unread posts will become read. Not only that, but if I decide to come to the forum, read a few topics, then leave, leaving some unread, they will be switched to read when I return. This doesn't happen on any phpbb forum I visit.
Another real nifty feature of phpbb too, is that when you look at an unread thread, all the posts you HAVEN'T read, will show up with a little orange post icon, while the read ones will have a blue one, so it's easier to go through and cut to the chase, without having to read old posts to find where you left off.
Not only that, but because it's free, and open source, I'm sure you can also find a whole bunch of mods to make the site that much cooler, and add a lot more functionality too.
I must say, I'm a mod on another medium-sized forum that uses phpbb, and it is much easier to use then this. :-/
Here's their little comparison chart thingy: