I've peaked at your signature code:
Code:
SOP rep:  [ URL="http://forums.sourceop.com/threads/123658-samhudson333-s-rep-thread"]http://forums.sourceop.com/threads/127197-samhudson333-s-second-rep-thread[/URL]
And it pretty much explains why. The first URL, is the page it goes to. While the second URL in the code is what text it'll display on the forums. The display text is correct, while you never changed the URL the user goes to, as such they still go back to your old rep thread.

Code:
SOP rep:  [ URL="http://forums.sourceop.com/threads/127197-samhudson333-s-second-rep-thread"]http://forums.sourceop.com/threads/127197-samhudson333-s-second-rep-thread[/URL]
^ 2 same URL's.. that's what you need. Though remember that in the beginning I put a space between [ and URL=" so I can show you the proper code.