I had the same problem few days ago. Setup was : 4 cards (5870s) on mobo, all with extender (16x and 1x). Ubuntu won't boot with a card on extender (Xorg failing) but will finally without. I had no issue in BIOS however.
The solution in my case was to directly connect the card with the (faulty?) extender on the mobo, leave the others with extender. (Actually, 2 cards up, 2 cards down on mobo, more space means also more vent)

I'm very curious about what caused that weird crash, if anyone got a clue...

I've just found the issue (after 3 days of troubleshooting) : I used a faulty PCI-e 16x extender that crashed the rig. Yes, it was a cheap eBay cable from KongKong BUT the other cables work (PCI-e 1x extender modded by me... which is basically cutting a little end of plastic) ! 
Thanks for the help I received from all members of this great forum and other fellow mining adventurers !

Hey there !
It seems I'm in same sh*thole 

My rig is 4x 5870s and fresh Ubuntu Natty.
I followed Inaba's HowTo.
Everything went fine (from steps 1 to 31).
On step #32 ($ sudo reboot), the rig reboot but won't load Ubuntu GUI (obviously an issue with X). Instead I got the Ubuntu logo and 5 red dots and automatic reboot or simple frozen black screen. If the latter appears then I still can access terminal with Ctrl+Alt+F1. The system asks for login+password. Once looged I try to start phoenix which only detect my CPU.
$ fglrxinfo returns
"Error: unable to open display (null)"
$ startx gives me a black screen again.

Help please !

LinuxCoin is a very light distro only designed for mining. I gave it a try, not much result tho' (kinda nothing actually, never got it to work)
Great concept, still need improvement imho.

I'm reading this forum for quite a time, did not register tho' (my bad...)
Now that I got a huge issue with my miners, I can't post in the appropriate section. IRC has been my salvation, but real-time solution does not offer the support of currently connected people nor documentated solution for others in the same case.
Get me out of Newb-section please ! My 9 5870s are looking at me with despair in their eyes...

what's your deal ?
pm me !

If I read of useful comment that solved my problem, then do I wish to show gratitude ?
False debate.
Need 5 post I guess  

I like the concept of having a proper Trademark (legally speaking : serving to identify the source of goods/service, with secondary meaning, widely interpreted/known by the public as one precise good/service)
Yet I disagree on copying the design of a regular gold-ish coin. If we create a new currency, why keep the old meaning of a coin (especially a virtual one). I feel the same way when a new website/service appears with old symbol for mail (the simple letter) or search (the looking glass). Let's do something new !
As for the Baht debate, is the national Thaïland currency symbol different (simple straight vertical line in middle of the B, cf Wikipedia) ?

I fully understand the restrictions concept to avoid spam issue, however posting 5 messages would lead to a long topic of useless stuff (... like the present one).
I did spend alot of time on this forum for documentation prior to mining installation. Now I got a huge problem, I cannot openly ask the community advice to solve it. Should I register sooner ? I certainly would with a clear restriction policy (like in top of forum, sticky annoucement, not only Newbie section).
Yet I find the log time pretty accurate to see if someone stay long enough on a forum to avoid hit'n'run poster.