Wil,
I dunno cept it's v.annoying. Tradesports (aka TradeBetX) use this message board software, so does a movie site I read, both work fine with this browser, hell its not that old. Also, as I said the test board at infopop works fine.
Anyway, I turned on IE browser script debugging option and here are the javascript errors:
Clicking on these tabs gives...
Line: 303
Char: 7
Error: Object doesn't support this property or method
Code: 0
So you think this is a Javascript method that does not work only in IE5? Why do all the other infopop boards work? I'm stumped.