Error in registration

I’m using WP 3.6 and I get this error when trying to register – http://screencast.com/t/IbZMTnsX

I get the error above but the registration is still successful.

I tried to deactivate some plugins that I think was having conflict but still get the error.

Has anyone experience this?

Thanks.

http://ww.wp.xz.cn/plugins/mingle/