User Reference Select List Broken

When adding a user select field, with select list option chosen, I get a warning:

Warning: Invalid argument supplied for foreach() in /home/dave/public_html/dave-cohen.com/modules/cck/content_admin.inc on line 705

Later, when adding a node, I see a textfield and not a select box. I also saw this warning:

Warning: Invalid argument supplied for foreach() in /home/dave/public_html/dave-cohen.com/modules/cck/userreference.module on line 71

If I type a name that is not a valid user, I get no error, but Anonymous is displayed. If I type a valid user name, things seem to work.