SPDIF disables itself overnight

SPDIF used to work flawlessly with WMC7 and Intel G620 integrated graphics. I only needed to set the SPDIF as default in the Via HD panel.

Since installing an HD 6450 video card I have to re-select this option everyday, or more if the HTPC stays in sleep mode for a long time. In fact the HTPC is always on & just goes to sleep when not used.

The other day I found an SPDIF setting in Control Panel > Sound and made it the default, but that made no difference.

Any suggestions on how to fix this?

The SPDIF is coming off a header on the mobo. The HD6450 has no SPDIF. I need SPDIF because my A/V receiver does not have HDMI inputs.

HDMI used to come off the mobo port & went to the HDTV. Now I'm using HDMI from the HD6450 to the HDTV.

The mobo is using the manufacturer's driver from their disc.
The HD6450 is using the latest driver from it's manufacturer's web site.

So it's SPDIF from the mobo & HDMI from the HD6450. I thought that might be an issue but it does work. It just does not "stick". This afternoon I turned on the PC & SPDIF was still enabled which surprised me. I thought maybe the order in which I tried & selected things might have made a difference. But then I turned of the PC & when it came back on the SPDIF was disabled in the Catalyst Control Center.

I'll see if there's a new sound driver for the mobo.

I've disabled the HD 6450 card's audio in the device manager.
I've confirmed with ECS that onboard video is automatically disabled when a graphic card is inserted into the mobo.
I've installed the latest sound driver from the ECS website.

SPDIF still gets disabled as the default setting in the Via HD audio deck after long periods of sleep, such as overnight.

Any suggestions?

Is there any registry hack that will keep SPDIF as the default?