Thanks, Ive now managed to get the SD card to be recognised. I used the same code as before, but changed it to FAT16:
diskutil partitionDisk /dev/disk1 1 MBRFormat "MS-DOS FAT16" "GAMEBUINO" 100%
It appears every time I try and do a standard format, the SD card stops working, but If I do this, It works once more.
So when the SD card has been formatted, there is one file with a .TRA extension. Its has a character in the title which looks like a downwards facing >
x>1.tra
when i copy the other HEX files across and boot up I get a very strange result. i copy the 12 files but 24 appear on the gamebuino (+1 extra for the .tra file). they all seem to be copies of the original hex files. All of them start with an underscore and end with the same downwards facing > and a 1. they are all also 4KB in size.
Ive re-checked on my computer and they are not there, even after another format, and emptying the trash (incase they are old deleted files) and using another programme:
http://faqintosh.com/risorse/en/sys/setrash/
to check that specific volume for undeleted rubbish. It couldn't find anything. Ive done various error checks on my computer and nothing has said I've damaged the SD card yet so Im assuming its working fine (especially now I can read from it).
Sorry to keep hassling you, and thats for all your advice