Ok, I've installed this modification on 6.5 without any problems.
There is however a script problem with 6.5 that I'm not sure how to work out. It doesn't seem to want to list the total topics or posts which is sort of puzzling, does anyone have any input?
And yes, that is the ONLY error that I had recieved... You can see my test board at:
http://www.promodtecnologies.com/cgi-bin/ubb/ultimatebb.cgi