Anyway, there's a potential bug, or rather.. an oversight.
Fixed, thanks!
Please do not use google captcha.
Use alternative.
Why? Recaptcha is a bit difficult, though effective. And they don't ban Tor or anything like that.
The problem is Tor likes to switch IP randomly, sometimes it happens while you are trying to solve the captcha. The captcha images are so slow to load sometimes (they fade in from white) so sometimes you run out of time. Also it's pretty hard, I had to try several times because I was getting "incorrect recaptcha".
I like to use noscript and a proxy here for obvious reasons: bitcoins and scammers don't mix well, so you want to take measures against it.