Picture freezes after a while

[wbree]

I have the PCH A200 and a Thecus N5550 NAS with a Gigabit wired network.
The problem is that after a half hour or so the picture and sound freezes. The A200 respond on "info" but pauzing, play, FFW etc not.
Network set in the PCH A200 is set on "auto". The file is a x264 6Gb movie.
The NAS doesn't give any error and should have a transferrate of > 100 MB/s.

I don't know if the problem is the A200 or the NAS?

Any ideas??