Thanks for your help. I've gone through the intructions again, here's some more detailed information about what is wrong.
I originally installed it on version 2.2.1, and it worked perfectly.
I upgraded to 2.2.2 and re-hacked, but now get problems.
Here is a link to my forumdisplay.php; maybe by looking you might know whats wrong?
My showthread.php just acts as normal.
The admin forum.php and search.php seem to be hacked correctly.
Thanks again for your help.