lost my conference theme and have errors

I've got COD running (still have a couple of errors to deal with (like the one below)). However, all of a sudden, the site wasn't pulling the conf theme css. When I go to admin/build/themes the conf theme (which I put in profiles/cod/themes as directed) doesn't show in the list of themes available. Is there somewhere else to define a theme for the conference?

Also, can anyone point me in the right direction about the following error when creating a new user:

warning: array_fill() [function.array-fill]: Number of elements must be positive in /afs/ir.stanford.edu/group/conf/cgi-bin/drupal/profiles/cod/modules/og/og.module on line 1613.
warning: implode() [function.implode]: Bad arguments. in /afs/ir.stanford.edu/group/conf/cgi-bin/drupal/profiles/cod/modules/og/og.module on line 1614.
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 DISTINCT(n.nid) FROM node n INNER JOIN node_access na ON na.nid = n.nid WHERE (na.grant_view >= 1 AND ((na.gid = 0 AND na.realm = 'all') OR (na.gid = 0 AND na.realm = 'og_public'))) AND ( n.nid IN ()) in /afs/ir.stanford.edu/group/conf/cgi-bin/drupal/includes/database.mysql.inc on line 172.
warning: Invalid argument supplied for foreach() in /afs/ir.stanford.edu/group/conf/cgi-bin/drupal/profiles/cod/modules/og/og.module on line 1620.

thanks.