I have the same physical setup that I had with my old Toshiba 30HF85 TV, i.e., an HDMI connection from the computer to the TV. That setup worked perfectly.
One thing that I think I remember is that the old tv was shown as a "TSB-85something" in Device Mangler, and I had to choose the playback as High Definition Audio separately. I cannot do that now, as that choice is grayed out. It shows the M370SL connected, but HiDef Audio cannot be chosen as a playback device.
I am playing with different drivers now.