I received a server error when trying to split a collaboration artist into two artist credits. This may have been been because one of the artists didn't exist in the database.
Any more specific details to replicate?
Looks like it might be the same as MBS-2107 ?
Yeah looks like it is.
I received a server error the first time, but when I tried to repeat it I got http://musicbrainz.org/edit/14479261.