Finally got it working after removing all instances of Sharepoint Forums, then continuing from step 2 above - don't know what happened, but it seemed to work in the end. Thanks for posting this solution, it's been invaluable!
Swarve
That's awesome - I've been banging my head up against a wall trying to get this installed for the last couple of days. Just one problem - when I attempt to add the web part, I get the error "Unable to add selected web part(s). Sharepoint Forums 1.2.0.0: The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT:0x80131040).
Any idea what this means and how I can resolve it?
Thanks in advance,
Swarve