looks like i got it to work. i put the 1GB card in the 7600 and used the formatting option in the SETUP pages to format the card, then went ahead and copied the OS update to the card and the unit is now updating.
before i was attempting to format the card in the mac with an MS-DOS format.
OUPDATE seems to be working now (it's 22% done).. so i think the card is OK.
however, the 64mb card still would not format in the machine.. but, at least this one does.