Many urls in the blog directory or subdirectories present that error. That same error appears when navigating to the blog itself. Picking various URLs for the directory produce the same error:
blog/wp-login.php
blog/wp-atom.php
blog/xmlrpc.php
blog/wp-config.php
blog/wp-admin/edit.php
blog/wp-admin/categories.php
blog/wp-admin/plugin-editor.php
Other errors:
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blog/wp-admin/menu.php
Produces:
Fatal error: Call to undefined function __() in /home/mydomain/public_html/mysubdomain/blog/wp-admin/menu.php on line 7
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blog/wp-admin/admin-db.php
produces blank browser page and source
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blog/wp-admin/xfn.js produces content of the .js file.
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blog/wp-admin/setup-config.php
produces
Sorry, I can’t write to the directory. You’ll have to either change the permissions on your WordPress directory or create your wp-config.php manually.
Maybe it’s a permissions problem. I will sift through this site looking for permissions info.
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blog/wp-admin/menu-header.php
produces
Fatal error: Call to undefined function get_admin_page_parent() in /home/mydomain/public_html/mysubdomain/blog/wp-admin/menu-header.php on line 6
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I am able to view individual image files.
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I am going to check permissions issues now but will be checking back here for other ideas.