The other reason can be that your ISP has the old version of the page cached, (ISP's will cache popular pages/websites to save on traffic costs).
To force a refresh from your ISP insert a ? as the last symbol in the URL you want, this works every time
Whatever you do don't assume that your post hasn't been accepeted, UBB (the software PPRuNe runs on) gives you a page for about 5 seconds telling you that your post has been accepted, it is extaordinarly rare for the post to "dissapear" if you have seen that page.
The other UBB handy hint is to highlight your whole post , just before pressing submit, then right click and copy it, then if you have typed in your password incorrectly, you don't have to type it in again, so many bulletin boards, so many passwords.