Never seen that message before
Just to check a few things:
> Did games stop working before updating firmware or after ? - If after, try an older Firmware & see if that fixes it
> Are Games that don't work 'Homebrew' or commercial ROMS (or are you having mixed results) ?
--- If Homebrew, maybe they need DLDI patching
--- If ROMS - possibly bad DUMP or got corrupted somehow, try re-downloading ROM & try again
--- If Both - got no idea, can only guess corruption
> When formatting - did you use Windows FORMAT or
Panasonic MicroSD Formatter ? - I believe Windows formatting can cause problems
> Have you tried removing the SAV file & letting game create new SAV (could it be corrupt SAV file) ?
> What make of SD card have you - a 'named' make or unknown 'Generic' card. Possibly problems with the MicroSD card - have you tried another SDCard ??