I also have problems with iTunes 6.0.5 (20) [on a mac PPC, with OS X 10.4.7]
I see my share in the iTunes sidebars but when I click on it to load the music it gets busy for a while then errors out with this message:
The shared music library “celas” is not accessible for an unknown reason. (-3259)
Check that any firewall software running on either the shared computer or this computer has been set to allow communication on port 3689.
However on another computer of mine [win2k sp4] with iTunes 184.108.40.206 (due to other problems updating does not work) can play that share fine.
The logs don’t show anything abnormal and nothing big is happening when I try to connect (meaning mt-daapd does not suddenly jumps to 100% CPU).
The computer running mt-daapd [0.2.4] is on OpenBSD 3.9 on i386. It is moslty idle.
To advertise the share I use the howl library rather than the built-in mDNS implementation.
Applying the patch to webserver.c available at http://trac.fireflymediaserver.org/changeset/1285 fixes the problem.