I have the same problem. The weird thing is the form doesn't get submited and throws a "please try again ..." error with orange border only in GOOGLE CHROME and IE 8 (didn't tried other IE versions). In Mozilla works fine. I started testing with older versions down the line until I reached version 4.1.2 which works fine in all browsers. Something happend at version 4.2 and up.
I deactivated all plugins and used the good old twenty-twelve theme just to be sure I limit the posibility of failure due to faulty code from other plugins I use along.