There have been only two occasions that I can think of where it failed to work
1) when the extensions directory was actually missing
(I will go add a picture of where it is - No, it's not a special place - it's the folder structure you see when you attach the kindle via USB - The FAT root
(/mnt/us when you attach via USBNETWORKING)
note that the USBNETWORKING application is not of the list of REQUIRED things.
2) When one of the - extensions config - files was wrongly line ended
. (DOS line endings)
There is a tool dos2unix that I have attached to post 3 to check this.
Worst case scenario you would simply swap the extensions into a backup folder (any, just make one) and then move them back one by one, see which one breaks the Launcher. Then let me know so I can document it or try to do something about it.
I updated the main docs to reflect this more clearly. thank you.