Paul, you're right:
My System update (BM 5 OS Update) shows 5.00.
If I manualy search for an update there's nothing. Perhaps I should leave it connected to the internet... but leaving a Windows System connected to the internet nonstop is like removing the doors from your house at home and invite some burglars :-)
I fixed the problem with multiple albums:
I edited the tags using iTunes and named "Album artist" identical as "Album name". Now that finaly seems to work!
EDIT:
Yesterday I checked "update software" and it downloaded an update - but after checking the software version it's still 5.00!? What's wrong here?