Cannot login to edit and publish my post

When I try to edit my first post which I saved and left in pending review mode, I cannot seem to login to edit and publish it. Here is the message I get when I attempt to access the wp-admin extension which worked just yesterday:

Warning: require_once(admin.php) [function.require-once]: failed to open stream: No such file or directory in /home/content/m/w/g/mwgmedia/html/wordpress/wp-admin/page.php on line 2

Fatal error: require_once() [function.require]: Failed opening required ‘admin.php’ (include_path=’.:/usr/local/php5/lib/php’) in /home/content/m/w/g/mwgmedia/html/wordpress/wp-admin/page.php on line 2

Any Ideas?