I have problems in Mediaportal with Swedish channels SVT1 and SVT2, the video sometimes freezes for a short second and shows some artifacts and at the same time sound stutters. All the other Canal+ (approx 30 channels) have no problems.
When I plug the same cable into Dreambox 7000 (very old) there is no problem.
What could be the problem ?
Here is my HTPC setup:

MediaPortal Version:
MediaPortal Skin: Blue3wide 1.1.00
Windows Version: XP Pro (SP3)
CPU Type: Intel Core2 Quad CPU Q9550 2.83GHz
HDD: Intel SSD X25 80GB
Memory: 4 BG
Motherboard: Gigabyte GA-E7AUM-DS2H
Video Card: NVIDIA GeForce 9400 (on motherboard)
Video Card Driver: 178.13
Sound Card: Realtek HD Audio
Sound Card AC3: Realtek HD Audio
Sound Card Driver: 5.10.06235
1. TV Card: TechnoTrend S2-3200
1. TV Card Type: DVB-S(2)
1. TV Card Driver:
MPEG2 Video Codec: MPC-MPEG-2 (Gabest)
MPEG2 Audio Codec: MPC-MPA Decoder Filter
h.264 Video Codec: Blank, there is no drop-down option
Satelite/CableTV Provider: DVB-S / Canal+
HTPC Case: Claritas
Cooling: Fans
Power Supply: Corsair HX 450
Remote: StreamZap
TV: Panasonic
TV - HTPC Connection: VGA <-> 5 RCA