Hmmm… that sounds like:
1. mt-daapd isn’t broken
2. iTunes on the PC isn’t broken
3. iTunes on the Mac isn’t broken
uhh… so what’s not working? Other than the fact that it isn’t working. :/
haven’t we eliminated everything?
Just for grins, have you tried disabling the firewall on the XP box, and disabling the firewall on the Fedora box? (is that /etc/init.d/iptables stop?)