Error when hit "Edit" in revision1 - you don't have permission to access this page

I have read the comments made about the unintuitive revision process ( http://projectpier.org/node/120 ) and agree:

What I don't understand is if this is the process by which one is supposed to introduce new versions of a file why there is even an "Edit" button in the Revisions that are below the current one.

When I hit the button in the Revision 1 area (and I am the administrator) I get an error message at the top of the page, "You don't have permission to access requested page". I don't see how I can't have a permission if anyone is going to and if no one can use this button what is it's purpose?

Just wondering. Thanks.