After upgrading a SharePoint 2010 installation to Service Pack 1, my public-facing site, to which Anonymous users should have full access to the Entire Web Site, started showing the following message anywhere it should have been showing content pulled from lists:
Access denied. You do not have permission to perform this action or access this resource.
We literally fixed this by logging in, going to Site Permissions and editing Anonymous Access:
Don’t change anything. Click OK.
Voila, everything worked again.
In our case, we had custom permissions applied on several other lists and pages. To fix these, we simply went to the affected page(s) and clicked “Edit Page.” This simple action fixed our issues and the site displayed correctly thereafter.
