What is the starting value for curStory? and starting value for storyTitle? and value of numberStory?
if curStory starts at 1, and numberStory is 5, then the first 2 times through the loop nothing will happen because curStory would be 2, then 3 - and you don't start setting the text fields until it gets to 4.
Also, it looks like you are trying to set up a menu of 5 titles, but your json array only has data for 4. And since the loop may not be doing anything the first two times it runs, then after that it may be setting text fields on the 3rd and 4th times through - and then running out of data in the array...
but I would need to see a little more code to know for sure...
(well, I see jayderyu beat me to it, lol)