MyTV: No Audio on WPTO group of ATSC channels (2 Viewers)

[vj950]

TV-Server Version: none
MediaPortal Version: 0.2.3.0
MediaPortal Skin: default
Windows Version: XP home SP2
CPU Type: Pentium 4
HDD:
Memory: 1 gb pc3200
Motherboard:
Motherboard Chipset:
Motherboard Bios:
Video Card: GeForce 7600GS
Video Card Driver:
Sound Card: integrated 7.1 channel
Sound Card AC3:
Sound Card Driver: realtek HD audio driver
1. TV Card: Hauppague HVR-950
1. TV Card Type: USB
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: purevideo
MPEG2 Audio Codec: purevideo
Satelite/CableTV Provider: OTA ATSC
HTPC Case:
Cooling:
Power Supply:
Remote: none
TV:
TV - HTPC Connection:

error description:
Ever since the installation of MP 0.2.3.0, there is no audio in WPTO group of OTA ATSC channels. The menu sound effects are present and all other channels work flawless, its only with these 5 channels the audio never works.

1. started mediaportal in fullscreen mode
2. went to MyTv
3. turn TV on
4. Started channel 14 prime (WPTO DT3) - no audio
5. Changed to channel 14 world (WPTO DT4) - no audio
4. changed to channel Fox 19 HD (WXIX DT) - no problem encountered
5. MP closed

Please help me resolve this problem. I'm not a very technical person
Thanks