Upgrade.php for 2.2 won’t run

After backing up, deleting old, and uploading new, I tried to access the upgrade tool at the wp-admin/upgrade.php

What appeared was this:

Warning: require_once(/home/tiffanyb/public_html/blog/wp-includes/wp-db.php) [function.require-once]: failed to open stream: No such file or directory in /home/tiffanyb/public_html/blog/wp-settings.php on line 100

Fatal error: require_once() [function.require]: Failed opening required ‘/home/tiffanyb/public_html/blog/wp-includes/wp-db.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/tiffanyb/public_html/blog/wp-settings.php on line 100

What’s wrong?? Thanks!