Thanks, for future reference I am using mac mini (intel) with OS X 10.4.9 and svn-1586 on the MSS+.
I was able to upgrade to iTunes 7.2.0.35 on the windows client which can see the MSS+ firefly server without any problem.
So nothing wrong with iTunes version and back to the mac. As there is no firewall and a direct connection to the MSS+, the only thing I can think of is that bonjour has been disabled aka the mDNSResponder process.
This is really strange as I just performed a fresh installation of mac OSX after upgrading my hard drive 2 weeks ago and I never disabled it.
I will check this later when I get my hands on the Mac.