Frank, did you ever find a solution to your problem?
I have the same unit as you, started getting an "out of memory" error and proceeded to delete what I thought were some unnecessary files. That pooched the card. I have been able to restore the card from a backup but need a larger card. I purchased a 16GB card and copied all files back but it does not work.
I would be happy to send you what I have but I don't suspect it will work when I can't get the 16GB card to work.
Hoping you found a solution.