PHP errors after 4.7 to 5.2 upgrade

I just upgraded my site from 4.7 to 5.2. Everything seemed to have gone well, except that I am now getting these php errors on the top of every node:

    * warning: Invalid argument supplied for foreach() in /var/www/old/modules/node/node.module on line 521.
    * warning: implode() [function.implode]: Bad arguments. in /var/www/old/modules/node/node.module on line 525.
    * user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1 query: node_load SELECT n.nid, n.vid, n.type, n.status, n.created, n.changed, n.comment, n.promote, n.sticky, r.timestamp AS revision_timestamp, r.title, r.body, r.teaser, r.log, r.format, u.uid, u.name, u.picture, u.data FROM node n INNER JOIN users u ON u.uid = n.uid INNER JOIN node_revisions r ON r.vid = n.vid WHERE in /var/www/old/includes/database.mysql.inc on line 172.

Any ideas what could be causing this?