We did an update quite a while ago to fix some major problems with firefox, and like Prince Karo said, it works pretty good normally. The caching issue is because it caches data-side actually. I don't think hard-clearing your cache really does anything except help you take the amount of time it uncache the data.
I have a working copy of the forums version 2.0 (these are 1.1), but they are in beta right now and so I'd kind of prefer to wait until the full version comes out later this month than introduce new bugs.
What browser are you using? If its a Windows browser I might be able to test it on the new forums to see how it runs (though the caching thing probably won't go away, even my code caches a lot of stuff since I don't like stressing the server with constant database draws).
Richard M.
Grimfang"Whisper"Xaeraes