That error happens because your browser is broken. I had the same issue because my image viewer assumed i.imgur would always serve images but they've recently been serving redirections and html (presumably to force people to see ads).
The obtuse message seems to be Firefox's fault, but even with Chromium or wget I just get an HTTP 429. "Too many requests" from an IP I have exclusive use of, which hasn't tried to access imgur in days. No, the site is just broken because some business knob decided that breaking the site might help revenue.