fatal error, dashboard not working

i was trying to get comments to show up on the homepage and somewhere along the lines i messed something up and am now getting this error message:

Warning: main(./wp-blog-header.php): failed to open stream: No such file or directory in /usr/home/aschrag/domains/arielschrag.com/public_html/press/wp-admin/index.php on line 4

Fatal error: main(): Failed opening required ‘./wp-blog-header.php’ (include_path=’.:/usr/local/lib/php’) in /usr/home/aschrag/domains/arielschrag.com/public_html/press/wp-admin/index.php on line 4

i haven’t moved any files from their original spots, only made slight changes to the index.php file – however i then deleted the changes i made and saved again and it did not resolve the error. every other part of WP seems to be operating fine it’s just in the dashboard

any help would be much appreciated..thanks