I have created a very bizarre and disturbing situation while attempting to get Home Sharing working on a new machine, and I am completely befuddled ...
Previously I had a working home network: a Netgear 7550 gateway for ATT DSL; ethernet cable to a Mac Pro 1,1 running Lion; wifi connection to several devices including a Macbook Air running Mavericks, an Apple TV 2nd Gen, and my girlfriend's PC and iPad. Everything worked fine (given ATT's pathetic 3Mbps DSL, all I can get here), including streaming music from iTunes on the Mac Pro to the ATV2 (with optical audio connection to stereo system).
Recently I replaced the Mac Pro 1,1 with a Mac Pro 4,1 running El Capitan (and upgraded Macbook Air to El Cap also). Things seemed ok until I tried streaming music from the new Mac Pro to my ATV2. After turning-on Home Sharing (in iTunes on the Mac Pro), at first the ATV2 said the music library couldn't be found, then it found it and played a few seconds of a song before going quiet (although the progress bar kept going as though all was fine). Then I started noticing that the wifi-connected devices complained they were "not connected to the internet". At one point, sleeping the Mac Pro allowed all the wifi devices to connect, and waking it made them lose connection. This is even after I turned off Home Sharing on the Mac Pro and rebooted it. (I must have been hallucinating, but it seemed at one time that waking the Mac Pro caused the wifi connections to fail - even with the ethernet cable unplugged from the Mac Pro !!)
Needless to say, I'm at a loss and would be thankful for any help. I have no idea how to proceed. One thought I have is that my wifi network is overwhelmed, and I'd be well-served by buying something like an Airport Express (given the slowness of my broadband connection, and with no devices newer than my 2011 Macbook Air, I doubt that the Airport Extreme is worthwhile for me); is this likely to solve my problem ?
Mac Pro, OS X El Capitan (10.11), 4,1
