same problem over here. It frequently happens as soon as several users
create metadata at the same time.
Our system administrator is looking for problems between internet- and
intranet-URL.
Our GeoNetwork 2.6.0 is available via intranet-URL and internet-URL, but we
must not create any metadata by using the intranet-URL. For creating
metadata we have to use the internet-URL.
We could not find out where the problem is exactly but it seems as if it has
to do with the use of an internet-URL and an intranet-URL for one
installation of GeoNetwork 2.6.0 at the same time.