Auto upgrade to WordPress 3.1.3 FAIL!

Hey guys, I just performed an auto upgrade to 3.1.3 like I do with all my wordpress sites, like I’ve done with this perticular wordpress site many times before but now I’m getting major errors.

SITE LINK:
https://www.bizwenipreprimary.net/blog/
ERROR:
Fatal error: Call to undefined function wp() in /home/bizwpre/public_html/blog/wp-blog-header.php on line 14

I’m also getting this error when I try logging in:
Fatal error: Call to undefined function get_option() in /home/bizwpre/public_html/blog/wp-admin/admin.php on line 32

I’ve checked with some of the same issues but none of the suggestions worked and my client is going to kill me when they find out it’s down and I cant fix it!!!

THINGS I’VE TRIED:
I’ve deleted the wp-config.php file but then it gave me this error:
Fatal error: Call to undefined function wp_die() in /home/bizwpre/public_html/blog/wp-load.php on line 52

I’ve tried renaming my Paid Theme’s folder, but no change.
I’ve tried changing the name of the plugin’s folder, but no change.

I have an old backup of the site, and can try get things up and running again from scratch, but the client has posted photo’s and articles and newsletters that I dont have a backup of now. So I’m hoping there’s another way.