I tried to upgrade from version 7 to the current level of version 9. I got this error. In searching all my files, I find no reference to DotNetGallery.
I restored from backups prior to when I attempted the upgrade and still get this error. I next have installed DotNetGallery in an attempt to eliminate the error. In doing the install, I found no existing references to the required entries for installing DotNetGallery. I am at a standstill. I tried everything I can think of and still get the same error page.