I have been successfully and happily using 4.18.3 for quite a while on my Mac (Tiger, 10.4.11).
As far as dowloading music by itself is concerned, it seems to work. But each and every time I tried to start the integrated player in order to check that the song I am downloading is the right one, it worked as well... but Frostwire suddenly quitted after a couple of seconds!
After many unsuccessful attempts, I finally re-downloaded 4.18.3, with which everytning is OK as previously, but it is a bit of a pity not to be able to use the latest improved version. Should anybody have an idea (and maybe a solution) about this problem?