Hello, beautiful people of Bitcoin.org.

I come to you for help regarding the problems I've been experiencing with my rig:

2x HD6990 (Asus)
Asus Crosshair formula IV
Corsair 1200W PSU
OS: Lubuntu 11.04 (Ubuntu with an LXDE desktop)
I am using poclbm as the miner.

I have read through and through all the Wiki, the forum and many obscure google searches and have not yet been able to find a solution.

Let me explain.

Before I bought the second 6990, it worked perfectly.
I was able to follow the brilliant guides on this forum, and set up a rig that produces about 1.5 BTC/day, so I went ahead and bought another 6990.
Thats when the problem started.
When I plugged the second 6990 to the motherboard (I didn't crossfire, obviously), Linux was not booting to desktop. I was getting just a black screen, and was unable to do anything except a hard reset to the computer.
I went ahead and started again, this time in recovery mode. I tried starting X server on failsafe, but that didn't work either, so I went ahead and deleted whichever xorg.conf files I had in /etc/X11/  .
This time the system did start, but since the xorg.conf file was gone, poclbm wasn't able to find and use my two 6990 for mining (it only saw the processor).
At this stage I ran "sudo aticonfig --initial -f --adapter=all" (with or without the -f, it didn't matter), and sure enough, xorg.conf was generated in all its beauty. (I did not yet reboot at this point.)
Trying to run "./poclbm.py" I saw that it was able to see the two Cayman cores (0 and 1) on the first 6990, but not the second one.
I rebooted the machine and was greeted by that same black screen from before.

Currently I have tried, numerous times, to install different ATI drivers. Both from ati.com and the repo's.
I have tried to find some reference as to X server making these problems with dual 6990 on ubuntu, but found nothing similar.

Running "aticonfig --list-adapters" does give me a list of all four 6990 cores on the system.
Running "lspci", I can see that the PCI bus given to the 6990s is the same as the one written in xorg.conf

At this point I'm stuck. The only way I'm able to log back into linux is if I delete the xorg.conf and start fresh.

Anyone here with two or three 6990, and mining on linux that can help?

Thanks for reading this far.

If there's any more info you need, let me know.