I had the same problem, took me a long time to understand what was wrong in the first place, since i'm a total newbie in the macos stuff. I finally managed to boot snow leopard with easybcd, and have my system working fine.
I replaced the default easybcd nst_mac.iso with the latest iboot iso (2.6) (which I obviously renamed to nst_mac.iso), rebooted and entered successfully my snow installation. The iboot iso reads the com.apple.boot.plist file from within its Preboot.dmg file, inside its extra folder. This boot.plist file there contains some flags that are necessary for my system, arch=i386 to boot snow with 32bit kernel and have all my drivers working fine(like the wireless netgear wg111v3), and PCIRootUID=1 to make my geforce gtx 260 work fully.
The iboot.iso has another com.apple.boot.plist file, outside of the preboot.dmg, in its extra folder, which is ignored (luckily cause it hasn't any useful flags there).
Iboot 2.6 uses the chameleon 2 rc5 r700 build.
Hope this all makes sense and it helps someone else out there.
(it would be nice if easybcd used the boot.plist file iboot uses, I think it covers a wide range of systems).