Are you using Chrome? Cause i have had this with several sites yesterday while using chrome. Not here on the forum though. And chrome is giving me a few more errors the last few days. And i heard from other people they are having those weird things with chrome. Mainly trying to go to a second page of something and keep on returning to the first page.
If your getting email notifications from a thread with certain special characters in the title, the link gets broken at those characters. So it reverts to sending you to the first page of the thread. A fix is to copy/paste the rest of the link into your browser address bar and then hit enter.