Well, I installed Ndless 3 to my Nspire today. Now the screen looks like that.
Details: I put a non-cx cas gbcemulator on my calculator and clicked it and then the screen froze. Then I removed the Ndless-map with the resources.tns with the Student Software on my computer.

Apparently that was a stupid thing to do:

Do not delete ndless/ndless_resources.tns as long as Ndless is installed, as it can cause a reboot-loop that can only be stopped with a complete reformat & OS reinstallation.

I've already tried all this:

If the device is a TI-Nspire CX or TI-Nspire CX CAS, begin by holding down the reset button. With the reset button held down, press and hold the [Doc] [Enter] and [EE] keys. Release all keys at the same time. The device will boot up as in the previous reset, but will display a menu with the following options. Please try options 1, 2, 3, and 4 in that order.

1. Cancel - The most non-intrusive reset option; no changes are made, the unit restarts.
2. Delete Operating System – The operating system will be deleted without deleting any documents.
3. Delete Document Folder Contents – This will delete the user’s documents, but will not delete the OS.
4. Complete Format – This will delete the OS and all documents for a total erase of memory.

I've tried with installing the newest OS (both from their homepage and the safe copy on my computer) but

I haven't tried to remove the battery since I only have a screwdriver for the upper ones.

So, what's next? 

Yes, since the previous options didn't work.

I think something like this has happened to me before. I guess you might have to unplug and replug the battery. You only need to unscrew the "upper screws" to remove the battery cover.

Yes I do confirm that I've had this bug on CX even without using Ndless.

Removing the battery was the only way for me to skip the "gray" screen.

So it's a bug.  Which means the warranty should cover it? (I'm guessing installing Ndless makes the warranty invalid. But after the complete format there shouldn't be any trace of Ndless..)


Or is it idiot proof to unplug and replug the battery?

Found the warranty. It says I've to try replacing the battery before I return the calculator.  The warranty also says it become invalid in case of improper service :s

And there's nothing about replacing the battery in the manual (it just says rechargeable AAA batteries is strictly forbidden and other useless stuff..)

I found a video about how to replug battery on TIs site link (Now I know you should unplug the white thingy from the calculator and not the cords from the battery, heh..)

But I don't find any videos or tips about how to unplug it. Help?

I've tried with installing the newest OS (both from their homepage and the safe copy on my computer) but

What happens exactly after OS reinstallation?

Hey everyone, I'm having the same problem too. The only thing is: I can't do the steps OP mentioned because they don't do anything.
I see the grey screen with a clock for some time but then it dissapears. Holding Doc+Enter+EE and pressing ON also doesn't do anything. Any advice?

Also, how the heck am I supposed to remove that battery?! That plug is so tiny. Would it be bad to pull hard on the cord to get it out?

For those with the same issue, could you please check whether the following alternative procedure found by simonsimons34 works for you?

• Hold the the following keys at boot time: Esc+Menu+Minus
• This brings the diagnostics menu. Then run the NAND tests (I don't know which option it is)
• Exit the diags software. The OS will hopefully boot normally.