I had the same experience. What had been a flawless
TV3 experience suddenly became what you described. I wonder if it has anything to do with the minor software update from a few days ago?
I would select a movie to play, a frame of the movie would pop on screen and then the forever wait spinner would spin. If I waited a very long time, I would see minor progress on the buffering bar. If I waited still longer, a bit of the video might start playing but then it would catch up to the (too) slow stream feeding the (pre)buffer.
At first, I thought it might be just the new movie I encoded, so I went back to stuff I knew had streamed just fine from prior views. Same effect. Then, I went to a small encode from a DVD (knowing this would be both small file size and smallish Mbps). Same effect.
I've got a wired network that has always worked fine. I checked the AEBS and tested streaming to other devices. All fine. Then, I did the simple thing: unplug the
TV3, wait about 30 seconds, plug it back in. This solved the problem (at least for now). If I was guessing about possible causes, I would guess there might be a bug in the
TV3 software that increasingly eats up the buffer space until there is hardly any left. Then, when you want to stream a film, it's trying to load it into what would be the equivalent of too-little buffer slower than it plays.
The unplug-wait-plug move probably clears the kludge out of the buffer memory. However, if this is a bug, it will likely repeat from similar use (probably leading to another unplug-wait-plug in the future). Otherwise, it may just be the classic case of needing to occasionally cold start tech to flush all of the memory. Try it and see if that solves your problem too.