It is not seeing some files, it should have mach_kernel in this listing.

However when I also add checking for correct partition signature

(http://lists.openbios.org/pipermail/openbios/2011-August/006618.html)

it seems to work

I am betting you are using the HFS+ file system with a HFS wrapper. This is a case I didn't test. Thanks for catching this bug. Could you send me a patch? Let me know if you need help with making a patch file.