Okay, I see what this is doing now.
When you make a post, the post will no longer just show up. It will now refresh the page (by it's self, and it's normal) and your post will be there. The issue is ajax is waiting for a response, and because the forum is looking for hte errors that are there, but are covered up, it times out as I have stated before.
So if you click on the new post button, click on a thread and read it, reply or whatever, then click the back arrow to return to the new post page, you will now have to click the back arrow button twice to get there.
I hate that we have to do this, but again, vBulletin is putting a bandaid over a bullet wound. this is a serious issue, but because they have a new version out that they want money for, they are only patching the old version...
As always, post any issues you see including if this reloading the page thing annoys you. The upside is, there should not be any double posting anymore...