I'm keep getting this: 'Fatal error: Call to undefined function WA_Auth_RulePasses()'

I keep getting this from my public pages on my site:

Fatal error: Call to undefined function WA_Auth_RulePasses() in file blah blah on line blah blah…

Basically, I have added some security show if statements to my pages to allow editing of SEO content (page title, keywords, description) where I have these areas display on the webpage they're associated to when the admin is logged into. They are just based on the bog standard PowerCMS edit on page method, but if the user is not logged in, then these areas are hidden and utilised in the SEO areas.

I can click to the page and the page displays correctly, if I then click to another page and then hit the back button, the error then appears. If I refresh the page, the error disappears and the page displays correctly.

I've added require_once( "../webassist/security_assist/helper_php.php" ); but this gives me more errors which also tell me the helper is only required the once!

One of the pages in question is attached to see if you can see anything that might be wrong.

Thanks.