Elaborating on what bunanson is saying, I'd be trying the Panasonic formatting tool and I'd select all the most demanding options, like Yes to erase, etc. (I forget what they are, but you'll figure out which is which). (Maybe I'm saying this because I don't know what the HP formatter is, but the Panasonic tool seems to get to the bottom of things!) (Also, I assume you're doing this with a card reader, not while inserted in the NIT.)