I had a similar issue. Using chrome://net-internals/#events I was able to see that my issue was due to some silent redirect. My get request was being fired in an onload script. The url was of the form, "http://example.com/inner-path" and the 301 was permanently redirecting to "/inner-path". To fix the issue I just changed the url to "/inner-path" and that fixed the issue. I still don't know why a script that worked a week ago was suddenly giving me issue... Hope this helps someone