WMVHD choppy in MP, fine in WMC

[Raytestrak]

MediaPortal Version: 0.2.3.0 + svn build 04-08-2008--05-05-Rev18584
MediaPortal Skin: Monochrome
Windows Version: Vista Ultimate
CPU Type: T9300
HDD: 160 GB 2,5" sata 5400 rpm
Memory: 4 GB
Motherboard: Aopen MP965-DR
Video Card: Aopen MP965-DR
Video Card Driver: 1.5.8
Sound Card: Aopen MP965-DR
Sound Card AC3: Aopen MP965-DR
Sound Card Driver:
1. TV Card: Yuan 770 / Avermedia a330
1. TV Card Type: Hybrid DVB-T / Analog
MPEG2 Video Codec: nVidia PureVideo
MPEG2 Audio Codec: AC3 Filter
h.264 Video Codec: CoreAVC
Satelite/CableTV Provider: Caiway
HTPC Case: Aopen MP965-DR
Cooling: Aopen MP965-DR
Power Supply: Aopen MP965-DR
Remote: Harmony 525
TV: Sharp LC37XD1E
TV - HTPC Connection: HDMI

Hi,

I have a weird problem. Almost everything works fine, even 1080p x264 runs smooth ... but I can't get WMVHD to run smoothly. There are pauzes every few seconds, even the sound stops. If I play the same wmvhd in windows media center, it works like a charm. Even my crappy xbox360 plays them flawlessly.
And it's not the intense scenes which give trouble, it's just weird. The bird scene from planet earth doesn't stutter for example, but the waterfall a scene before it does.

I'm using the internal media portal player, because I want everything to be controlled by my harmony and external players don't work very good. Any idea how to fix this?

*edit:

I'm streaming files over my network. As I said, 1080p x264 content: no problem. WMVHD: choppy. Locally WMVHD's play fine too. So it's a combination of things. It isn't just the network, since I can play the files in windows media center from my network without any hic-ups.

*edit2:

Found the solution, it was a vista service designed for multimedia streaming. Killed the multimedia class service and it works like a charm now!

Mark's Blog : Vista Multimedia Playback and Network Throughput