After attempting to remove a Discogs URL via the new entity fields ("External Links") on the Edit Release page:

"Remove relationship
Relationship: Stain [1] by Living Colour [2] has a Discogs page at http://www.discogs.com/release/1338864 [info] [3]"

[1] http://musicbrainz.org/release/2ecd8ae7-2f3f-3176-9110-81d8665c343f
[2] http://musicbrainz.org/artist/dc6f8c1f-626b-42b0-9115-7e66ae4cecd6
[3] http://musicbrainz.org/url/a1e16ba1-b74c-48b2-94f2-57076de0723a

I get the following error (see attachment):
"Failed query: 'SELECT 1 FROM editor WHERE id = ? FOR UPDATE' (328771) DBD::Pg::st execute failed: ERROR: current transaction is aborted, commands ignored until end of transaction block at lib/Sql.pm line 107, <$fh> line 1..."

Perhaps relevant: I re-added the same URL as a new entity in the same editing session (I mistakenly thought the one I was removing was for a different edition).