Audio Delay when changing channel

[przymul]

TV-Server Version:
MediaPortal Version: 1.0.0.0
MediaPortal Skin: default
Windows Version: XP SP2
CPU Type: Athlon XP 2600+
HDD: Seagate 20gb + Samsung 80gb
Memory: 1gb DDR1
Motherboard: ASRock K7NF2-RAID
Video Card: Winfast GeForce 6800XT
Video Card Driver: latest
Sound Card: CMedia CMI9761A 5.1 channel AC'97 audio codec (onboard)
Sound Card AC3:
Sound Card Driver: latest
1. TV Card: KNC-1 TV-Station DVR Analog
1. TV Card Type: analog
1. TV Card Driver: latest
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: MPV Decoder
MPEG2 Audio Codec: MPA Decoder
h.264 Video Codec: ffdshow
Satelite/CableTV Provider:
HTPC Case:
Cooling:
Power Supply:
Remote: Medion X10
TV: Philips 32' CRT
TV - HTPC Connection: S-Video

When i changing channels i have video and after 3-5 second i get audio. There isn't any a/v sync problems.
I discovered that when i changing to channels that have stereo audio there is no delay but if the channel have only mono audio it is.

PS. There is no logs because when test tool is working i'm getting some kind of windows error.