Professor Layton save data corrupted

Keep getting this after playing the game,The game seems to play ok and saves then when I try to use the rom after shutting down the ds it says save data corrupted.Can anyone help or suggest fix ?Sorry if already covered but couldn't find it,using RGF 6.70 (R4 clones) because everything has run on this in the past,thanks.

http://forum.romulation.net/index.php?topic=57120.0Keep all issues with Layton in one topic please