This module has been great for me using Zencart 1.5.1 however it looks like something needs updating for Zencart 1.5.4

When installed in 1.5.4 an error message is generated when a customer tries to login again or create an account. Looks like something needs changing in the header_php files in includes/modules/pages/login and includes/modules/pages/create_account_success folders. I restored the original 1.5.4 header_php files and the error message disappeared so I think it is the header_php.php files that are the problem.

I am using the Responsive all business template but don't think this relates to the issue.
My test site is at canadaflagshop.com/demo
Can you help?
Robert