it happened to me twice already. When i turn my Casio fx991ES PLUS on, it is reset, i have not done that! I have to set everything again, complex numbers, LineIO, memory is deleted. If that happens once a week, I can live with that, but my experience with electronics is, things can get worse, like every day or even during work.
Is it something with batteries? I noticed it happend both times after I moved from place to place. Lower temperatures? Pushing of something on the spot, where batteries are? It is 1,5 years old.
What can be wrong?