I have a file paylines.txt added inside the folder named TextFiles which resides inside the Resources folder of my iOS project in Xcod
paylines.txt
TextFiles
Resources
I was also having the same problem. The Solution i found is ( in xcode 4.x):
Go to : Target -> "Build Phases" -> "copy bundle Resources" Then add that particular file here. If that file is already added , delete it and add it again.
clean the project and RUN. It works. :)