Mkv + dts = jerky (1 Viewer)

[scorpie]

MediaPortal Version: 1.1 RC1
MediaPortal Skin: pureHD
Windows Version: XP SP3
CPU Type: Quad 9300
HDD:
Memory: 3GIG
Motherboard:asusp5b
Video Card: 8800GTS
Video Card Driver: the last one
Sound Card:
Sound Card AC3:
Sound Card Driver:
1. TV Card:
1. TV Card Type:
1. TV Card Driver:
2. TV Card:
2. TV Card Type:
2. TV Card Driver:
3. TV Card:
3. TV Card Type:
3. TV Card Driver:
4. TV Card:
4. TV Card Type:
4. TV Card Driver:
MPEG2 Video Codec:
MPEG2 Audio Codec:
h.264 Video Codec: coreave/powerdvd9 I tried both
Satelite/CableTV Provider:
HTPC Case:
Cooling:
Power Supply:
Remote:
TV:
TV - HTPC Connection:

HI,

hope someone can help me.

I have problems to play this files properly. I have a lot of dropped frames, really annoying to watch this movies.

No problems with mkv with ac3 sound.

I did some testing to find this out. mediaplayer 11 was not able to play this files, after installation of the ac3 filter mp11 plays these files well - judder-free.
It is better in MP as well (choose ac3 for audio under codecs), but not perfect. Still have some juddering.

Is there a way to fix this, maybe some settings in the ac3 filter?

Thanks for your help
scorpie