I was streaming mp3s from my FreeNAS 7 fileserver over CIFS the other day to a MusicZones zone controller and every two minutes or so there would be a break in the audio, but not when I was pulling Internet radio directly to the zone. Mind you this was over 802.11g, and there was no EM interference. Interestingly, my wired zone controllers which are on standard 100Mbps Ethernet over CAT5 do not experience these audio breaks.
Turns out lowering the Send Buffer Size and the Receive Buffer Size from the default 64240, to 8192 did the trick. Inspired by looking at old FreeNAS and Openfiler smb.conf files.