Anyone ever use this faux-Excel App? I used it on the 84+SE a few times, but found it quite fiddly and didn't get into it much. Still, I downloaded the CSE version for the sake of completeness, and I think today is the first time I ran it. Then when I selected Quit from its menu, the calculator returned to normal except...

The following keys would not work: APPS, PRGM, all the top row of Graphing functions and their <2nd> uses, <2nd>-DRAW, and <2nd>-Mem. Interestingly, the <ALPHA>-F key shortcuts did still work, and I think pretty much everything else, but I had no access to graphing, programs, Apps, or the reset options in the Mem menu. I was thinking the reset button on the back might be my only option, but couldn't remember whether that would croak the Archive memory too, so planned first to connect to the PC and see if I could backup the program I was working on today, then reset. But by chance I found scrolling the Entry History a run command for the aforementioned program before the glitch occurred. So I could check whether it was still there! The program ran fine, and since part of its operation is to graph the function, I finally got to see my graph screen again. Even more remarkably, it seemed to heal all the ills in my calculator: the inactive buttons now work again!

I mention all this
* in case anyone knows why this would happen, or how to prevent it,
* to warn you that, so far as I can tell, it was CelSheet that caused it.

Is it an ASM program? A hybrid-BASIC program?
If it's an ASM program, I believe there are ways to disable some keys, so maybe they weren't reenabled. If this happens again, I believe that 2nd+MODE should reenable those keys, or at least it does for disabling ON breaks.
I'm not sure if hybrid-BASIC can purposefully disable keys, though.

I believe that it is an application released by TI, which should in theory be next to awesome since they made the calculator and the program. This is quite an interesting thing that happens; I am going to try and recreate it...

CelSheet is an assembly App released by TI.

OldMathTeacher: It sounds like CelSheet installed what is called a hook and failed to uninstall it when you quit CelSheet. A hook is a section of code that runs when specific events happen. For example, a keyhook runs when you press a key on the keypad, and can do things like veto the keypress (making it seem to the OS that it never occurred) or change which key the calculator thinks was pressed. An AppChangeHook is triggered when you're about to change "Apps": not just the Apps in the Apps menu, but built-in "Apps" like the graphscreen, the memory menu, and so on. It would be very helpful if you could find a way to replicate your results so I can report this to my contacts in TI's R&D team.

I wondered if it had something to do with hooks (although all I know of them is from the Doors threads, and can't pretend to understand fully). I'd be wary of replicating this result tbh, but I might just back up everything and give it a try later on (family meal first, though!).

Oh, huh. I've never heard of it. :/

That's because you have a CSE. I believe it doesn't come preinstalled on the CSE, probably because it was not written when the CSE was out. It is preinstalled on monochrome models however and is usually one of the first thing you uninstall when you need space.