My 1080p movies tended to stutter and when I bought a new PC the other week I thought the extra power might help (quad core 9550, 3870x2 graphics etc) however, there was no improvement.
I stream over my electrical mains using Comtrend Powerline adapters which I understood were pretty much plug and play. They are, but since I had no manual for them, I didn't know they weren't happy when used in surge protected multiway adaptors.
Changing the Powerline straight into a socket instead of the multiway and hey presto - perfect streaming of every movie.
Maybe this is common knowledge, but I thought I'd share it anyway for others who might have similar setups.