I installed the Apple 5770 card in my Mac Pro 3,1. Works great with my monitor on the DVI port. However I have a second monitor and it won't work on either of the mini displayports. I've tried the displayport -> DVI adapter, and the displayport -> HDMI adapter. I've also tried putting both monitors on the displayports with adapters. The only configuration that works is 1 monitor on the DVI port. Any ideas on this?
Also, Mini DisplayPort can be tricky to install correctly. You need to push on the adapter until essentially ALL of the metal part disappears inside the connector.