No sound via HDMI to Yamaha A/V receiver

[Razorblade]

I have a Yamaha RX-V465 A/V receiver connected to my TV via HDMI. The Yamaha does have a HDMI repeater for splitting up audio and video.
When I connect my Fedora 10 box directly to the TV via HDMI there's video and sound. So my setup seems to be ok.
But as soon as I connect my Fedora box to the A/V receiver via HDMI I do not get any sound towards the receiver. The receiver tells me that there's no audio input signal. But video is working fine then.

mplayer -ao alsa:device=hdmi putsomemp3here runs fine without errors.

Yamaha support says this might be a hardware related issue and I should apply the latest firmware for my HDMI equipment.
It's not a hardware related issue because when I boot windows on this box, I have video and sound via HDMI to my Yamaha.

It's an ASUS M3N78-VM with the latest NVIDIA drivers (185 I think) from the NVIDIA page.
Kernel is: 2.6.27.9-159.fc10.x86_64
I can not upgrade to latest kernel because HDMI audio is not working then.