Upgrade 7.1.3 problem. Cant register on the site.

Hello all. I just upgraded my site to 7.1.3. and I just can't register on the site. Instead its showing message that its a spam registration. Any inputs on how to fix this? I am using following mods for join form.
http://www.boonex.com/m/Site_s_Join
& Drake field in join form
http://www.boonex.com/forums/topic/China-is-invading-help-me-with-form-field-validation.htm

It worked when I disabled "Smart antispam check". What does this function do?

This is some JavaScript check, if you have some JS error on join page this check can become broken.