AC3Problem within MP (1 Viewer)

[sebrock]

TV-Server Version:
MediaPortal Version: 0.2.2.0
MediaPortal Skin: BlueWide
Windows Version: WinXP PRO SP2
CPU Type: AMD64 3500+
HDD: Samsung 300gb
Memory: 512 mb cheap shit
Motherboard: MSI K9GM2-FID
Motherboard Chipset: nForce 4
Motherboard Bios:
Video Card: Geforce 6150
Video Card Driver: 91.47
Sound Card: Realtek HD Audio
Sound Card AC3: Realtek HD Audio
Sound Card Driver:
1. TV Card: Hauppauge 1300
1. TV Card Type: Hybrid
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:
Satelite/CableTV Provider:
HTPC Case: Silverstone LC16M
Cooling:
Power Supply:
Remote:
TV: HDTV 27" / Projector
TV - HTPC Connection: DVI-D


I use ffdshow and ac3filter to get my 5.1 sound. Problem is that the AC3filter is only activated in some of my movies. If I play the very same file outside of MP (i.e windows mediaplayer) the ac3filter works perfect. Why is MP making this not work on all my movies?