Originally reported a long time ago in
http://bugs.musicbrainz.org/ticket/2644
and NGS seems to have a similar problem.
select count

from url where ref_count = 0; gives 29489, which is too high (I count 7705 URLs with no relationships). Either the ref counts aren't being updated properly, or we're not using them at all and should just make them all zero or null or something (and later remove the column).
l_url_work being the wrong way round strikes again... The number should actually be 1429