Try going here, sign in with your normal info. https://www.joeuser.com/
Go to your account tab, then images tab, upload there. Give it a little time to take effect elsewhere.
If that gives the same error, you could try a few things.
Things like installing the latest version of Adobe Flash player. Or try a different browser. Or, if you're using IE11, try loading the site in compatibility mode.
That can be done by hitting the gear, top right, choose Compatibility View settings, add the site, click close. Page will reload, try again.