Guest role doing more than one created (document issue)

[Dean Birkett, módosítva 12 év-val korábban]

I'm hoping this is an easy one for you!

We have a public website with no login requirements to view certain documents. When you log in then you can access other document areas, that guests cannot view.

This all works, however if you aren't logged into the website, and you open one of the public accessible documents, then it opens perfectly.
However, if you log into the website, and click on the same document, then you receive an internal server error, "An error occurred while accessing the requested resource."

I'm a little confused as to why this is happening, I would have thought that it would take the baseline "Guest" role and add to it.

Any ideas what is going wrong?

Thanks!