TV has small speed ups (1 Viewer)

[Atreides]

MediaPortal Version: 1.0.1
MediaPortal Skin: Blue3Wide
Windows Version: Vista x64
CPU Type: Athlon Dual core 3.0 Ghz
HDD: 2 Tera Bytes
Memory: 3 gigs Corsair
Motherboard:
Video Card: Nvidia Geforce 8800 GTS
Video Card Driver:
Sound Card:
Sound Card AC3:
Sound Card Driver:
1. TV Card: Hauppauge HVR-1600
1. TV Card Type: Analog\ATSC
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: ffdshow
Satelite/CableTV Provider:
HTPC Case:
Cooling:
Power Supply: 750
Remote: Hauppauge
TV: Philips 1080p
TV - HTPC Connection: DVI-HDMI

Hey guys
I have a weird problem with my TV server. The video speeds up and then goes back to normal every few seconds. It is insanely annoying, and I do not know what it is. The sound stays the same and it does not speed up at all, only the video. I would appreciate any help on this. Thanks