If you are using now JSONP instead of text, the file will be loaded as javascript code, so if contents are not valid javascript code it will fail.
Surround data with a global variable assignation or a function call:
window.variable = "_DATA_"; // or
functionName("_DATA_");
If _DATA_ are JSON format, then you don’t need surround with quotes, otherwise you’ll need to use “_DATA_” because without quotes it will not be valid javascript syntax.