Hi dhew
I had a similar issue as well – Firefly would initially appear in my iTunes window then disappear intermittently. Sometimes it just wouldn’t show up and the whole thing was pretty random and unreliable.
That particular problem turned out to be my wireless router (a D-Link). I had to enable IGMP (sometimes called multicast) which was turned off by default.
It would be worth checking that out – the router’s administration interface should lead you to it.
Now it’s up and working like a treat.
Hope that helps
Cheers