This really isn't a difficult thing to do, but since I needed to go sniffing around for clues to figure it out, I thought posting a tutorial would be a good idea.

1. Do NOT let your DS lose power! No unplugging the battery!
   
2. Have a Slot 1 flashcard
3. Charge your battery
   
4. Run NoFlashMe (downloadable here)
5. Ignore anything that says "your DS isn't patched" or "short this pin" and press Start

It's that simple. Whatever broke your menus was able to run without the pin shorting you need to install FlashMe, so no need to short any pins to fix them either.

 

[cvskid]

This really isn't a difficult thing to do, but since I needed to go sniffing around for clues to figure it out, I thought posting a tutorial would be a good idea.

1. Do NOT let your DS lose power! No unplugging the battery!
   
2. Have a Slot 1 flashcard
3. Charge your battery
   
4. Run NoFlashMe (downloadable here)
5. Ignore anything that says "your DS isn't patched" or "short this pin" and press Start

It's that simple. Whatever broke your menus was able to run without the pin shorting you need to install FlashMe, so no need to short any pins to fix them either.

Would you be able to use that for twilightmenu on a 3ds to install a pictochat and or download play that is missing?

 

[alivebacon]

Would you be able to use that for twilightmenu on a 3ds to install a pictochat and or download play that is missing?

1. You can find good .nds files of the 2 online
2. You can get dumps of the DSi versions of them if you make a nand backup of a dsi.
3. this needs a ds/dslite
4. flashme always has the risk of bricking said ds/dslite if you fuck it up

 

[Konwalia]

So I have this problem, only I have never modded anything in my life so it's actually difficult to fix! My DS Lite is completely original so I am trying to understand what happened here, and what I need to do to fix it... I guess it won't fix itself with time, right?

1. Could it be that it was caused by me inserting a reproduction cart into my DS Lite? I bought 3 used games that I didn't recognise as non-genuine, but can a cart actually mess up my console menus like this?

2. I've made a start on the Wiki and it says not to use NoflashMe on a DS Lite (the page about FlashMe, I cannot post links yet). Will running NoflashMe make any changes to a system that has never had FlashMe or any unofficial software installed?

 

[Ryccardo]

1. Could it be that it was caused by me inserting a reproduction cart into my DS Lite? I bought 3 used games that I didn't recognise as non-genuine, but can a cart actually mess up my console menus like this?

It could - once upon a time there were true DS bootlegs, nowadays they are bottom barrel flashcards with the microSD literally taped in, in any case arbitrary code execution is possible and DS malware is a thing - that said it's extremely unlikely!

2. I've made a start on the Wiki and it says not to use NoflashMe on a DS Lite (the page about FlashMe, I cannot post links yet). Will running NoflashMe make any changes to a system that has never had FlashMe or any unofficial software installed?

Yes - Noflashme, pretty much, reflashes your console (well, wifi card) with the official firmware, it doesn't really care for what's there now; there also are multiple versions of Noflashme and, just like on most other gaming and otherwise products, it's rarely a good idea to downgrade below the factory-installed version, because they tend to add support for minor but possibly critical component changes!

 

[Konwalia]

Grazie mille Ryccardo Nel frattempo ho capito che devo scaricare nofmlite, la versione di noflashme per il DS Lite.

So additional steps for a total noob like myself, who had to google what a flashcart was:

- order an R4 card, with accompanying micro SD card and a micro-SD-to-USB-converter so that you can put downloaded files on it. There are also brands other than R4.
- download nofmlite.nds (for DS lite) from the website linked in the OP
- plug micro SD/USB chimera into your PC, Youtube will tell you how to format it and set it up. Copy the .nds file onto the inserted flashdrive.
- insert micro SD back into R4 flashcart and run nofmlite on your DS Lite. Make sure you don't run out of power like OP mentioned.

Bonus: you now have the knowledge and equipment to install homebrews and other files of your choice onto your DS, but I think I'll give that a rest for now so that I don't accidentally brick it

--------------------- MERGED ---------------------------

Yes - Noflashme, pretty much, reflashes your console (well, wifi card) with the official firmware, it doesn't really care for what's there now; there also are multiple versions of Noflashme and, just like on most other gaming and otherwise products, it's rarely a good idea to downgrade below the factory-installed version, because they tend to add support for minor but possibly critical component changes!

You know what's weird though? My WFC still works, when accessed in-game. Also both multi-card and single-card play work, as long as the other DS is the one doing download play. I simply can't access the menu anymore.