ATV will not stream my home videos

I have both an ATV2 and an ATV3. Running OS X 10.4.4 I have my home/ripped movies on an external drive connected to an iMac 27. The ATV2 which is in the basement works flawlessly every time. The ATV3 which is on a shelf next to a flat screen TV upstairs works flawlessly SOME days (even weeks) then will not stream my home videos at all for days/weeks. I can still stream Netflix when it will not work. I have tried swapping the 2 for the 3 to no avail. I have tried moving the ATV to different spots (within reach of the cables). I always get a full strength signal no matter where I put it.

Is it a rogue bluetooth signal knocking it out? Tried lots of things.... no iPhones in the room.... etc.... The most frustrating thing is that sometimes it works great.... and then for no apparent reason will not work at all. Never gets past the spinning ball. And if it does get to the first scean of the movie it will stream about 30 seconds of it and then stop and never stream any more.