TI89 worked before battery change, now screen flickering and in and out black areas? Advice?

So the TI89 was full operational and then batteries died. So I changed both backup battery and brand new set of rechargechargeable AAAs. Now when I turn the calculator parts of the screen work but there is flickering and dark areas that flicker in and out. Is there a period of recharging the calc must go through or is this a hardware issue?