I am using fire fox 3.5.3 on a pretty decent Firebird desktop machine that is just a few months old and which uses Vista 64 bit.
The core of the issue I am having is that the power bar freezes randomly. I have done a fair bit of messing around etc and nothing seems to work.
I know the game is in beta, so if the problem is not on my end, don't worry about it; I am sure it will be fixed when it goes "gold".