No problemo!
The F is for failure.
That means that something has locked the card on that block. Some gamesaves do this im affraid. I don't think it's because of the chip, cause i have a chip to.
I use to solve this by backup one save at a time on another card to finaly get the card to function again. Very irritating.
If you can't solve the problem at all, then return the damn card and get a new to try.
Don't think i can help you more than this im affraid.
Hope you'll get it to work. Have phun