Newsletters Not Being Sent

I've been trying to get the SimpleNews Digest module to work, and it is not working. I have checked my system logs and find the following errors logged in this chronological order. It seems to me the SQL query must be returning some kind of null result, but I don't know why. To my knowledge I have nodes that match all of this criteria. Posting the bug now, but I'll do a bit more of my own debugging afterwards.

implode() [function.implode]: Invalid arguments passed in /public_html/hrmyouthnetwork.org/modules/simplenews_digest/simplenews_digest.module on line 344.

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 ') AND n.type IN ('event','job_posting','memberprofile','orgprofile','story') AND' at line 1 query: SELECT DISTINCT n.nid, n.type, n.title from node n INNER JOIN term_node t ON n.nid = t.nid WHERE t.tid IN () AND n.type IN ('event','job_posting','memberprofile','orgprofile','story') AND n.created >= 1222941600 AND n.created < 1223027999 AND n.status = 1 ORDER BY n.created DESC in /public_html/hrmyouthnetwork.org/includes/database.mysql.inc on line 172.

array_fill() [function.array-fill]: Number of elements must be positive in /public_html/hrmyouthnetwork.org/modules/simplenews_digest/simplenews_digest.module on line 344.