vB4 Really Weird Redirect Issue - Help?

We recently moved from a single server to two server set up with replication. Since then we've been running into a very odd issue in vB. Sometimes when you click on a link, it'll take you to an entirely different link... but only in Firefox. That's the only major browser, anyway. I think someone said it happened in an old AOL browser too. Obviously, this is a problem because the forums are virtually unusable in a major browser.

I have never seen this before and the hosts have been unable to make any headway on their end. I'm hoping someone here might have some insight as to what might be causing this, or what even my first point of attack in troubleshooting this should be.

Here's an example:
Clicked on
http://www.toonzone.net/forums/cafe...iscussion-thread-post4423761.html#post4423761

Ended up on
http://www.toonzone.net/forums/termite-terrace-trading-post/28862-aap-opening.html#post4423761

Clicked on
http://www.toonzone.net/forums/dc-a...lease-discussion-spoilers-17.html#post4419981

Ended up on
http://www.toonzone.net/forums/dc-a...-original-animated-character.html#post4419981


Our cookies contain the server ID.
cookie server id: rbqn02h01rwmsession
cookie server id: rbqn03h01rwmsession

We suspect the issue involves something with the 03 server. Though I can't confirm that with complete certainty. Sometimes you'll click on a link starting from the 02 server and end up on the wrong page on the 03 server. Sometimes you'll click on a link from the 02 server and still end up on the wrong page on the 02 server.

We do still have vbseo installed, which I don't think is the source of the issue, but isn't helping in troubleshooting. So, my next steps are going to be disabling it and removing the mod rewrites from htaccess so that I can test these threads without its rewrites in place.

When we have users clear out their cookies and cache entirely, it resolves the issue for a short while, but it does return. I still have no idea why it's only Firefox users that are having this issue.

As I said, my next step is to remove the rewrites and disable vbseo entirely to see what happens. But if anyone has any insight or thoughts as to what might be happening here, please feel free to share. It'd be greatly appreciated.