So, what you should do is switch to a standard theme, clear out your error logs so that all these theme related errors are gone, and then re-load the register user page and see what error occurs.
Your page is getting errors at least from what I have looked at. Those errors need to be identified and corrected. If they are being caused by third party plugins or themes there is really nothing we can do to help. If they are Zenphoto errors then we need to see exactly the circumstances that cause them because, as we have said, we are not able to reproduce the situation on our installations.