Forumhome upgrade parsing problem

Greetings!

I'm running a test upgrade from 3.5.3 to 3.6 on my test box. Everything's going relatively smoothly, but I have a small problem with the "go to last post" feature when viewing the forum homepage.

If I mouseover a thread title, the link is parsing correctly. But if I click it, I get this URL:

testbox/forum/showthread.php?p=0#post0

instead of the correctly parsed URL:

testbox/forum/showthread.php?p=299263#post299263

I've reverted the forumhome and forumdisplay templates, but it still remains.

Any advice much appreciated.