I just plugged my Macbook Pro into my Yamaha receiver using a Toslink cable with optical digital audio jack purchased from the Mac Store. But every time I turn the volume up even a little, my receiver shuts off to protect itself.

I checked Sound under System Preferences, and sure enough, my Output Volume is set to the maximum setting. While the digital audio jack is plugged into my MBP, the slider is grayed out, so I can't lower it. I tried unplugging the digital audio jack and lowering the Volume Output, but as soon as I plugged it back in, it went back to the maximum setting.

Surely, there must be a way to play my MBP through my stereo at a decent volume level without blowing out my receiver. Does anyone know how?