After you press the DVD source button, you lose the 7.1 analog input so you're likely getting audio via optical or coaxial at that point. If you press "7.1D" again right after that, do you lose video again?
If it were my system, here are the things I'd check:
- Verify that the Blu-ray video input is going to DVI1 (and not DVI2, for example).
- Verify that the DVI output is connected to the TV.
- Verify that the TV is on that specific HDMI or DVI input.
- Verify that the 7.1 Direct input on the 990 is set to the DVI1 video input (again, and not DVI2, for example).
- Compare it to the settings for the DVD input (which cannot use the 7.1 Direct audio input but can use the same video input).
I asked about the remote because of item 3 on that list - wanted to make sure the TV hadn't gotten switched to the wrong input via a macro of some sort.