And what virus scanner? Perhaps it's simply a false positive based on heuristics or the virus tool is not that great to begin with and needs a signature update...
I've never seen this happen before when installing FB4 (which I've installed many times). It was a file named "users\user\appdata\local\temp\b59a.tmp". Has Adobe's server been hacked?
This may not sound very nice but I doubt Adobe is really keeping a close eye on it considering how they've mismanaged and neglected Flex/Flash for so long. I'd like to know if there is a proper download site with a correct checksum available...
Or, let me put it another way: If you're confident it's just a false positive, why don't you go ahead and try it out yourself? heh heh