Using second graphics card messed things up

[Joas87]

Hi guys,

I'm having some trouble with my new setup. Everything worked fine until I connected monitors to my second GPU. These things happened:

30 inch monitor on card #1 sometimes gave a max resolution of 800x600
USB 3.0 ports on the front stopped working
Mouse and keyboard didn't work
Monitors did not work on the second card

Right now I have two monitors connected to card #1 (Display Port) and they are working fine. My mouse and keyboard are working fine as well. Only thing that stopped working is usb 3.0, but that's not a big concern.

These are components I use:
ASUS P9X79 Deluxe
2x Radeon HD 7870 (Club 3d Royalking) connected with a Crossfire bridge

Since all that happened when I started using the second graphics card, there is probably a problem there. Do you have any idea what it could be?

 

[Meepz]

The graphics card will be disabled at first, go to bios

 

[Joas87]

GPU-z says: ATI Crossfire Enabled (2 GPUs) and I can see both the cards in device manager.

I'm trying to set up a 4 monitor setup, but I can't connect a monitor to the second card. I just now connected the 3rd monitor (HDMI) to card #1 and that worked. Is it a problem (for the performance) to connect 4 monitors to one card?

The usb 3.0 ports are still not working, could this be a driver problem? They have worked before, but after connecting monitors to card #2 the ports stopped working.

edit: Connected the 4th monitor and it works just fine