This has now been resolved thanks to the wonderfully speedy people in the Firefox development community. See http://www.activeinboxhq.com/blog/2013/02/27/firefox-20-is-a-ok/
A handful of you are on Firefox 20, which is only the beta release right now (it’s not mainstream), but in my eyes it’s a fire breathing dragon.
For some reason, and I think it’s a bug with Firefox, they’ve decided our website is broken. This means you can’t access http://www.activeinboxhq.com, because it declares “Corrupted Content Error”; and by extension, ActiveInbox cannot reach our server to log you into your Plus account.
I’ve filed a bug with Mozilla, at https://bugzilla.mozilla.org/show_bug.cgi?id=845273.
However, as Firefox 20 draws closer to conclusion, I’ll get progressively more ferocious in trying to slay said dragon, even if it means we have to assume responsibility at our end.
In the meantime, if you can avoid using beta Firefox with ActiveInbox, that would be super!
This was written by Andy Mitchell