Something's wrong with your copy of the game. Did you accidentally get it wet or
something?

The same thing happened with me too when i finish the game it said the end and then save
then it says "the gamefile has been erased"and then new game.

I know how to solve this problem. First,remove the appearance of color changing on your
desktop that sometimes may cause our games while playing so hard logging. Anyway if you
not yet get find out how to play pokemon nds so fast, i suggest that (for laptop)remove
sometimes the plug-in your charging tool & (for mac/windows pc)put your pc always
connected in wifi internet broadband switch then here it goes.tada.hope i help anyone of
you.
(if not worked 1 of this,just turndown all things in your desktop that making annoying
your playing games into illegal logging like deforestation of making scanning of your
files by windows desktop. (xxd