Hello...
I have problem too..I`m installing LawlessPPC 10.5.4 on my computer but no luck...

AMD Phenom 8450 X3
Abit AX78 (AMD770+SB600 Chipsets)
80GB Seagate SATA (AHCI Enabled in BIOS)
HIS HD 3650 512 MB PCIe (Using DVI2VGA adapter)
AC97 onboard sound
Installing process...OK

my problem is get a corrupted/garbled a whole screen soon after booting...but the OS seems working normal..I can hear sound coming from my speaker (a man telling "Mac OS Ten bla..bla..bla..)

The OS is working normal (no garbled/corrupted screen) if boot in save mode (-x)

help me please LawlessPPC...sorry for my bad english