Can't detect secondary display card

Hi,

I've just replaced my motherboard - I've now got an Asus A8N SLI Deluxe.

I use two graphics cards - both identical Geforce 8600 GTS to drive a dual monitor setup - one per card. I don't bother having SLI active - one card per monitor is just fine. :)

Any way, I've plugged both into my new mobo, but when I boot, I'm only detecting one of them.

The mobo has one of these single/dual card selector cards. I've tried this both ways around and it doesn't seem to make a difference.

I've not got the SLI bridge on top as I'm not planning to use SLI.

Anybody got any ideas?

Cheers.

Oh - worth mentioning - both cards work. :)