Your problem is the NForceATA.kext.
I also have a MB witn nforce3 (KN8) and this is what worked for me.
Go to:

http://osx86.wikidot.com/known-issues#toc10

Following the instructions there, DELETE the AppleNForceATA.kext, rebuild ISO and reburn. When you get to the installer, DON'T choose the AppleNForceATA.kext under the drivers section. Choose the AppleVIAATA.kext and it should install nicesely.
If you can, set apart a small partition for restoring the DVD, that way you will not waste DVDs experimenting.
Good luck! :-D