hi
Daemon did you have pc_efi installed on loader?
I have phenom 9500 and always with efi instant reboot when loads efi emulator, I had to modify 10.5.2 iso to boot with old bootloader and install old bootloader after install and modify some kexts. I tried with to diferent mobos (amd 690G and nforce4) and the same result.
If your mobo works with pc_efi with phenom, maybe I will be use pc_efi with phenom...
thanks it advance

How to install on Phenom
http://www.infinitemac.com/comments.php?DiscussionID=978&page=1#Item_1

Daemon

It looks like your system specs are close to mine... what distro did you use?

specs:

CPU: AMD Athlon 64 X2 AM2 6400+ Black, 3.2GHz
MOBO: MSI K9A2 Platinum AMD RD790FX Phenom (http://tinyurl.com/69dsfy)
Chipset: AMD 790FX chipset (AMD 790FX + SB600)
RAM: 4GB Mushkin HP2-6400 DDR2 800MHz Memory
HDD: 500GB S-ATA II 7200 RPM on SATA-1
VID: ATI Radeon HD3870 512MB x 2 (with crossfire cables)
CDRW: Internal DVD+CD Rewritable Combo Drive 16X52X32X52 (Primary Master)
DVDR: ASUS Internal SATA DVD+/- RW + CDRW Rewritable Drive (Primary Slave)
SOUND: Creative Sound Blaster X-Fi Xtreme Audio 7.1 Retail Edition
NET: Onboard Gigabit (10/100/1000Mbps) PCI Network Card

I have kinda Install problem:
Install disk: 10.5.2 v2 Zephyroth
Hardware: cpu: Opteron170
Mobo: DFI NF4 Ultra-D
HDD: IDE 250Gb Maxtor
VGA: Galaxy 8800gt 512Mb

Problem detail:
If I boot with install disk, system will boot normally.
Without install disk, I am getting cpu panic which says: " Unable to find driver for this platform: \"ACPI\" .\n"@/Volumes/disk1s2/leo_xnu/xnu-1228/iokit/Kernel/IOPlatformExpert.cpp:1405

Can somebody help me with this problem?

Update:

I found a solution. I havent installed LAN card drivers, and my system booted normally.
Also AppleACPIPlatform.kext has dependecies which results in kernel panic if, like in this example a specific hardware is installed.