Ha... I have another one for you, though from discussions I've had with the admin of another forum which recently upgraded to the same software version it too appears to be un-fixable.
Open a forum section, click on the very first thread you see (the one at the top of the list).
Click on the little "previous" link, as though you want to go to the next newer post in the list. Where once upon a time one would see a message stating that there were no previous topics in this section, one is now "wrapped" around to the oldest post in the section.

For example, load the "welcome" thread at the top of this section, and hit Previous. You should find yourself on a topic started by Chris S., back in 2002. Incidentally, Chris's thread appears on page 49 of this section.
