My Casio CFX-9850 calculator has a little problem... When I try to draw a graphic, even with a simple equation Y=2 (for eg.) a MEM ERROR appears. I can see in the manual that it has something to do with the calculator's memory. I have deleted some programmes and now with 1300 Bytes free it still does not work. It worked with less memory before why this problem now? Do I need more? what could it be?
NOTE: II've an exame next week and I cant lose all the programes

Thnks for helping.