mysql_real_escape_string(): 23 is not a valid MySQL-Link resource - Multi-DB Error?

I have Multi-DB up and running (I thought) fine. But when I go to the User Listing I get this error at the top:

Warning: mysql_real_escape_string(): 23 is not a valid MySQL-Link resource in /.../public_html/wp-includes/wp-db.php on line 785

I did some searching and found there are sometimes problems with the blogs directory plugin, but that is not installed. I do have the autoblog plugin installed though, and I did see some problems with feedwordpress, so I thought it might be related.

Any thoughts? Thanks!