DVI display shuts down when PC is connected to home theater

[Nnnooo]

Weird problem, I couldn´t come up with better topic...

I have following setup in the same room:
-PC with DCI connected display
-5.1 speaker with home theater amplifier and video projector

I would like to connect my PC to the home theater system with HDMI cable. When projector is on, everything works fine and I can see PC´s picture on the screen and on the display. But for some reason, if I connect PC to the amplifier when projector is off, PC´s display turns off automatically.
[strike][/strike]
Of course I would like to use my speakers also when the projector is off, so this is really annoing problem. I can´t figure out why the DVI display turns off every time when I connect the computer to the amplifier and the projector is off at the same time.

Any ideas?

 

[Nnnooo]

Any thoughts?

Or is it just some weird HDMI's feature...