I have two identical video cards right now. Xubuntu will boot up no problem if I only have one card installed. If I install the 2nd card it will just hang midway thru the loading screen. Regardless of which card I use and which position on the motherboard, it will freeze if I have both installed.

I've tried installing the proprietary drivers, both fglrx and fglrx-updates, still freezes in the same spot. Uninstalled those and went back to the default ones. The only way I can get a terminal is by booting into failsafe mode.

Booting using 13.10 i386 on a USB stick gives me some errors related to what I think is the 2nd video card:

[drm:r600_ring_test] ERROR radeon: ring 1 test failed (scratch(0x850C)=0xCAFEDEAD)

[drm:r600_dma_ring_test] ERROR radeon: ring 3 test failed (0x02FFFF6B)

radeon 0000:0200.2 disabling GPU acceleration"