get_core_checksums() error when updating to 3.7

I just tried updating to 3.7 and it’s failing.

When I manually update via FTP, it seems like nothing takes. When I go back to the site it still shows it’s on version 3.6.1 and prompts for 3.7 upgrade. This is an endless loop.

When I try to do an automatic update via the Admin panel, I get this error:

Fatal error: Call to undefined function get_core_checksums() in /xxxxx/xxxxx/xxxxx/wp-admin/includes/class-wp-upgrader.php on line 1526

Never had a problem upgrading before this new 3.7 package. Any ideas? Anybody else seeing this? I have tried deactivating all my plugins and still get the same results.