Macbook Pro / grub 2 errors -any ideas

[HiDeHo]

I have a
Macbook Pro: 13": October 2011
processor: 2.4GHz Intel Core i5
Memory(ram): 4GB 1333 MHZ DDR3
HDD: 500gb

i have set up and installed rEFInd bootloader and have installed Linux mint on my hdd.

I setup a pupptlinux frugal install and setup the grub 2 to boot from the puppy install.

I boot the puppy and it works find first time. then when i shutdown and try to reboot the puppy install i get an error that "the puppy main.sfs file can't be found". if i reinstall the puppy main.sfs file it will work again for the first boot.

i tried several different puppylinux versions with the same result.
when trying to run pfis=fsck it cant run a fix on the main.sfs as it cant detect it.
I think somehow the puppy main sfs file is becoming corrupted on shutdown.

would anyone have any ideas on this.

another related post about my computer is click here