MM_insert behavior and Captcha

Hi there,
I'm struggling to integrate your products and am trying to create a custom user registration system. I have created the initial registration form in Security Assist and followed all of the instructions for making the password SAH1 encrypted in your solution recipe videos. securityassist/

I then followed the instructions on for modifying an existing form on the CSS Form Builder support page. I discovered that my registration form DID insert the records into my database - which was great. But here's what's NOT working:

The MM_insert behavior isn't working correctly. When I try a test registration with the same user name instead of telling me that the user name is replicated, I get that the Captcha isn't correct. So somehow this is conflicting. How do I correctly do this? (MM_insert was the fix for a checking for unique user name in the Security Assist videos.)

Also - I would like to apply a Cookie to save the data on the page in case the user gets the Captcha wrong, I don't want them to repeat filling in all of the form field data. How can I retain this data? I have the Cookies Toolkit.

Thanks!