bhambob on "Version 4.5.2 causing PHP errors"

Just installed 4.5.2 and now we are receiving incessant PHP errors. No changes have been made to our website. We have had our own session management for ages but now when we get to the session_start() we get the following error:

session_start(): Cannot send session cookie - headers already sent by (output started at /var/www/html/wp-includes/class.wp-styles.php:237)

This NEVER occurred before we upgraded from 4.5 to 4.5.2.

Try deleting the old wp-includes folder and replace it with a fresh copy. Download a fresh copy of the WordPress .zip file to your computer, unzip it, and use that to copy up wp-includes folder.

And I was so hopeful... Before making any change to production I did a file compare between the class.wp-styles.php installed and the one I extracted from a downloaded zip file. They are identical. Other ideas?

We are getting pummeled by this problem, hundreds and hundreds of errors are raised each day. This was never an issue before we moved from 4.5 to 4.5.2.

Can I get some help with this or not? If not, how do I back up to version 4.5?