I've found the "fix". The package in Karmic uses the deprecated libmusicbrainz version 2 instead of 3 (the package of libmusicbrainz 2 is called libmusicbrainz4 in Ubuntu).
Jaunty switched from version 2 to 3, which introduced this bug. Now Karmic switched back, which "solves" this bug again. I've opened another bug report #455461, which explains why this is even worse than before.
I've found the "fix". The package in Karmic uses the deprecated libmusicbrainz version 2 instead of 3 (the package of libmusicbrainz 2 is called libmusicbrainz4 in Ubuntu).
Jaunty switched from version 2 to 3, which introduced this bug. Now Karmic switched back, which "solves" this bug again. I've opened another bug report #455461, which explains why this is even worse than before.