SQL Error and PHP error

Hello

I got 5.6 running, I get the following error, when submitting a comment. I tried to fix it in the node.module file (hack it), but it didn't work. Would be great if, you could give me a hint.

* warning: Invalid argument supplied for foreach() in /home/httpd/vhosts/rapsli.ch/httpdocs/drupal/modules/node/node.module on line 521.
* warning: implode() [function.implode]: Bad arguments. in /home/httpd/vhosts/rapsli.ch/httpdocs/drupal/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: 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 /home/httpd/vhosts/rapsli.ch/httpdocs/drupal/includes/database.mysql.inc on line 172.