I've not seen that when I've flashed, and as I didn't write the bit which does the flashing, it's difficult for me to do anything about it.

Some questions, though:

• The 770's connected directly to a USB port on the Mac, not through a hub or anything? (It should be connected directly)
• The 770 hasn't booted completely and the MMC card mounted on the Mac? (It should be sat with a screen showing nothing but the USB icon IIRC)
• What version of Mac OS X do you have? (I'd say it should be 10.3 or above, but haven't tested on anything below 10.3)
• You've got a PPC Mac, not an Intel one? (flasher-2.0.macosx is a PPC binary, not sure how well it'll work under Rosetta)
• What happens if you run it as root?

Any help available will be solely dependent on the amount of information you give, saying "I get this error" is useful, admittedly - but what's the 770 doing? what's the Mac doing? what's the Mac running? etc. etc. are all pertinent questions.

Cheers,

Andrew