No DD/DTS when resoulution set to 1080p (1 Viewer)

[daveleebond]

MediaPortal Version: 1.1.1.0
MediaPortal Skin: StreamedMP
Windows Version: Win7 64bit
CPU Type: Phenom x3 @ 2.6
HDD:
Memory: 4GB
Motherboard:
Video Card: Ati 4770
Video Card Driver: Cats 10.7
Sound Card: HDMI pasthrough
Sound Card AC3:
Sound Card Driver:
1. TV Card:
1. TV Card Type:
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: SAF 4
MPEG2 Audio Codec: SAF 4
h.264 Video Codec: SAF 4
Satelite/CableTV Provider:
HTPC Case:
Cooling:
Power Supply:
Remote:
TV:
TV - HTPC Connection: HDMI


Bit weird but here goes.

If I set my desktop res to 720p, can play DD/DTS fine through HDMI to my Sony SRTDH510->HDMI->TV.

If I switch to 1080, loose DD/DTS but can still play music and plain old xvids/divx's.

Have swapped over my HDMI cables but stil the same.

If played through MPC-HC@1080p works fine????

Doing my nut it, please can someone help.