WAV Volume to NIL after channel change (1 Viewer)

[zanlation]

TV-Server Version: RC2 (latest SVN)
MediaPortal Version: RC2 (latest SVN)
MediaPortal Skin: PureVision 1.2 4:3
Windows Version: Windows XP Pro SP3
CPU Type: AMD Althon64 4800+
HDD: Samsung Spinpoint 500Gb
Memory: Patriot 2048MB PC2-6400 800MHz DDR2 RAM
Motherboard: Gigabyte GA-MA78GM-S2H R1.0
Video Card: Sapphire HD3450
Video Card Driver: Catalyst 8.8
Sound Card: onboard
Sound Card AC3:
Sound Card Driver: Realtek HD 2.03
1. TV Card: Leadtek Winfast PVR-3200H
1. TV Card Type:
1. TV Card Driver:
2. TV Card: DigitalNOW Dual DVB-T PCI
MPEG2 Video Codec: Cyperlink PowerDVD 8 Ultra
MPEG2 Audio Codec: Cyperlink PowerDVD 8 Ultra
h.264 Video Codec: ffdshow (build 20080909)
Satelite/CableTV Provider:
HTPC Case: Silverstone GD-01MX
Cooling: AMD Standard
Power Supply: Seasonic 430W
Remote: Logitech 525
TV: JVC CRT
TV - HTPC Connection: S-video

I am experiencing a strange sound problem. Sometimes when I change channel the sound drops out. When I close MP and go have a look at the volume mixer the WAV is at the lowest level, but not mute.

Has anyone experienced this problem before?