My suggestion: Definitely try to check with firefox on a Win box and/or on a *Nix Box aswell. Then variate the browsers (maybe on a mac it works with another browser? vice versa with a different O/S?). Experiment for a little bit and see if you see a pattern developing.

Also, in the firefox readme file, it should tell you where your Browser ID is located. I also don't have Firefox installed at the current time so I'm trying to help as best as I can. The Help/Readme file should help you locate your Browser ID. Well, report back with your findings and PM me if you need more assistance/a better explanation of what we're talking about.