Did you tried to disable pxe boot rom and minimize roms to load when the bios boot? Sometimes there isn't enough ram left. Usually the ram is limited to very tiny amount, less then a 1 megabyte for option roms. This is what I know with the older BIOS. In the new UEFI it may not so limited. However I wonder how 4 video cards can work anyway? But it seems there is a malfunction in the bios from the video card. From wikipedia: other ROMs can be located from segments C8000 all the way up to E0000. It's only about 120-131 kbytes??
Link: http://en.wikipedia.org/wiki/Option_ROMWarning: Spoiler! (Click to show)
The cause of the problem is that in order to be PC compatible, which is limited to read-only memory to 128th This is true for any motherboard with PC compatible BIOS.
In the common configurations, a newer AGP card (such as a Geforce 4) will require 64K ROM, so that you only left 64K option ROM space to work with. Many SCSI, NIC with PXE IDE RAID can so easily another 40-64K of option ROM space.
By design, the option ROM should shrink to a smaller run time code after the initialization code has been executed. For example, some Adaptec cards will require 32K to initialize. Then shrink to 12K at run time, while some GeForce 4 cards require 64K to initialize and never let go. Please check with the device manufacturer for the latest firmware upgrade or ask if they have made available a smaller Option ROM. Again, this is a limitation of the PC compatible specification and not a failure of the motherboard BIOS.
The bios from my hd 6950 is 64 kbyte I think it shrink to less kbyte because I also have a crossfire but I have disabled pxe rom and raid rom option.Edited by Recursion - 5/9/13 at 9:35am