Volume not responding after Dolby Digital (1 Viewer)

[hjbaard]

TV-Server Version: 1.0.0.0
MediaPortal Version: 1.0.0.0
MediaPortal Skin: Monochrome
Windows Version: Vista 32bit home premium SP1
CPU Type: AMD Athlon 64 X2 Dual Core 5000+
HDD: Samsung H501LJ (500 GB)
Memory: 2 GB
Motherboard: Asus M2A-VM HDMI
Video Card: NVIDIA GeForce 8600 GT (Asus EN8600GT SILENT/HTDP/256M)
Video Card Driver: NVidia Version 178.24
Sound Card: on board (SPDIF)
Sound Card AC3:
Sound Card Driver:
1. TV Card: FloppyDTV
1. TV Card Type: DVB-C
1. TV Card Driver: Integrated Driver 4.5.N
2. TV Card: FloppyDTV
2. TV Card Type: DVB-C
2. TV Card Driver: Integrated Driver 4.5.N
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: CyberLink Video/SP Decoder
MPEG2 Audio Codec: Microsoft MPEG-1/DD Audio Decoder
h.264 Video Codec: CyberLink H.264/AVC Decoder
Satelite/CableTV Provider: ZIGGO
HTPC Case: OrigenAE H6 HTPC Zwart
Cooling:
Power Supply: Tagan 380W Super Silent
Remote: Gyration
TV: Plasma 42"
TV - HTPC Connection: VGA

When I watch a movie with Dolby Digital on, I have to control the volume with my amplifier (I'm using SPDIF), which is ok. But when turning back to view live tv for example in pro logic I sometimes can't control the volume within MP anymore. It seems stuck to the last volume value before going to Dolby Digital!

The only way to make it work again is to reboot my HTPC (rebooting MP has no effect).

Anyone know how to fix this? Or is this a bug in MP?