from http://bugs.musicbrainz.org/ticket/5421 which has a number of attachments and comments trying to figure out the problem

I started adding releases again after approximately 3 month of absence.
I follow the guideline http://wiki.musicbrainz.org/How_To_Add_Disc_IDs like usuarl in order to generate a TOC with picard and then add a new release with this TOC or attach it to an existing release.

So with a particular release:
http://musicbrainz.org/bare/cdlookup.html?id=7W6v1CnPB5PWwrqt5_9mzfqGuos-&tracks=99&toc=1+99+375+...+150+150...+150
I get this:
''No release found with the given Disc ID 7W6v1CnPB5PWwrqt5_9mzfqGuos-. Please try again.''

Instead of the usual:
''MusicBrainz doesn't currently have any CDs which have this TOC: ... ''

I also don't have the option to add this TOC (or ID) to another or a new release (wich I normally have at this page)
I am logged in and I only have the problem with this particular release. Others work fine.