Hi,
Sorry - I missed this reply. Still getting this issue on Safari Version 8.0.4 (10600.4.10.7), OS X version 10.10.2 (14C2513)
To give a little more info, when I visit the site in this browser clicking sign in brings up a dialog with the gmail email I was using - but it asks for a password. I never got to a point where I was asked for a password after the attempted login, but your system seems to have my email and some password. I'm resetting that password since I have no idea what it is or how secure it is.
On a private Safari window though, I get the same issue as before trying to log in.
(FYI I've also emailed you, probably better to discuss there instead of in this old thread)
EDIT: Probably mistaken about the password, sorry for the confusion - I think I did sign up with a different browser.