I'm using the linuxcoin on a USB stick and I've got 4 5830's in an ASUS Crosshair IV Extreme. Cool board, BTW.
Anyways, the problem I'm having is that poclbm (lets say) find's 3 cards.
root@linuxcoin:/opt/miners/poclbm# python poclbm.py
No device specified or device not found, use -d to specify one of the following
 AMD Phenom(tm) II X4 955 Processor
... similarly, aticonfig:
root@linuxcoin:/home/user# aticonfig --list-adapters
* 0. 01:00.0 ATI Radeon HD 5800 Series
1. 07:00.0 ATI Radeon HD 5800 Series
2. 09:00.0 ATI Radeon HD 5800 Series
* - Default adapter
AMDOverdriveCtrl is a lilttle more complex ... it finds "9" ... but it seems that it's finding 3 ... 3 times.
Anoyingly, lspci only finds 3 cards as well. Is this a BIOS issue or somesuch? I'm positive that I had 4 boards running before it moved to it's final resting place --- and I have reseated all the cards.