JSON.parse thinks my JSON is a function ?

JSON.parse thinks my JSON is a function ?

I'm afraid this kind of question has probably been asked 1000 times. So I will keep this short.

Here is my json:
{"Q1":{"months":{"Feb":"52.26","Jan":"53.50","March":"65.70"}}}

JQuery JSON.parse seems to think it is a function. I get a javascript error which comes from isFunction().

Can anyone help me out spotting what is wrong with the JSON? I've tried simplifying it, I can't see the issue.

Thanks for your help.