Unfortunately the "format error" messages are generally a result from a player being hacked to show more memory than it physically has stored on it.
There has been a lot of members who have a similar problem to yours. Did you buy it from eBay?
My best suggestion is to go through the steps mentioned here -->
How To: Removing Memory Hack.
That should hopefully remove the memory and should eliminate the 'format error' messages.
Hopefully that helps.