Manual Upgrade

After uploading the new files and trying to access wp-admin, I get this error…what do I do now?

Warning: main(/home/nasttr5/public_html/wp-includes/default-constants.php) [function.main]: failed to open stream: No such file or directory in /home/nasttr5/public_html/wp-settings.php on line 20

Warning: main(/home/nasttr5/public_html/wp-includes/default-constants.php) [function.main]: failed to open stream: No such file or directory in /home/nasttr5/public_html/wp-settings.php on line 20

Fatal error: main() [function.require]: Failed opening required ‘/home/nasttr5/public_html/wp-includes/default-constants.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/nasttr5/public_html/wp-settings.php on line 20