I'm using a TI-84+
1. If I hit [2nd] then [mem] it does nothing. Both keys work for all other functions. This has never worked for me, but I was always able to work around it.
2. Until now; for some reason when I try to graph anything lately it gives me ERR: UNDEFINED. Even simple functions like y=x. I figure a reset would fix this, but I can't reset because of #1.
UPDATE: Fixed #2.
UPDATE: Fixed #1