I got the same problem as here.I have Acer 5520G(AMD TurionX2,MCP67 works with modified AppleNforceATA.AppleVIAATA 32bit from Leopard...).
I want to update to 10.6.8 using Combo update but without success.

WE can't install lagacy kernel pkg because of amd_insn_patcher from the package.(libSystem.B.dylib and dyld don't need to patch in 32bit system).So I don't use the packed but only the kernel.Of course you can use amd_insn_patcher to patch anything else.

Change boot flag with -v arch=i386 busratio=9 idlehalt=0.

And it stops at ...Still waiting for root device.
I got this error before because of MCP67 IDE but now..i don;t know.
Help me to fix it pls!