murcel,
this is not a bug, but by design 
LinuxMCE supports multiple tags values per tag type, i.e. you can have a million titles associated to a media file.
i understand that. It makes sense in conjunction to the performer or writer/composer.
But then its a one way? As soon as the media is added to LMCE, i am forced to use the webadmin for tagging?
And...it does not really tag it, it is adding the tags to the database....
That is strange, in days i was using LMCE instead of Dianemo, i hadn't that trouble at all.
And what about the composer field - why is it automatically filled with the album tag....i don't believe that is by design, is it?
from what i understand, the tags, which i change in lmce should be written back
taken from:
http://wiki.linuxmce.org/index.php/MetaData_HandlingMarc