I recently had the chance to work on a problem concerning permission to access a specific web page in SharePoint 2010.
The error message that almost all of the users were getting was the generic “accessed denied” but using the Check permission button I could verify that the users had at least read permissions to access the site.
Playing along with the permissions I noticed that users having Contributor rights were able to see the page while those with Read permissions did not. I then stumbled on this forum post which perfectly described my situation.
The solution proposed by one of the users was to enable the permission “Browse Directories – Enumerate files and folders in a Web site using SharePoint Designer and Web DAV interfaces.” for the Read access level permission.
So there you go, enabling Browse directories did the trick!