Does PageSecurity have any issues with W3C caching

W3C works by pre-empting the whole WordPress load process and serving up a compiled file instead. As a result, it can conflict with other plugins that use redirect techniques.

I’m not sure if there is a way to make the two plugins work totally seamlessly together, but have you tried using Page Security’s “Replace” mode for your protection? That might do the trick.

To use replace instead of redirect:

1. From your admin go to Settings > Page Security
2. Set “Access Denied” pages for both Authenticated Users and Anonymous Users (you may need to create a new page if you don’t have one already).
3. Next to “Protection Type”, select the “Replace” option.
4. Save your changes

This will use a completely different technique for showing Access Denied messages. Instead of doing any kind of redirect, it will stay on the same URL (no redirect) but load up the content from the Access Denied page instead of the protected content.