iTunes 10 add to library very slow

I upgraded to lion and iTunes 10.5 on 3 iMacs. I created a clean iTunes library and added my 51000 songs (all my cd collection) that are stored on a network disk. I can play and search fast however, when it comes to "Add to library..." it is now taking an incredible amount of time. It does work but very slowly. I have copied the network contents to one of the iMacs and loaded iTunes again - same problem! This is definitely a problem with the new version of iTunes. I have even removed all the smart playlists and turned of all the options but this does not help.

Is anybody else experiencing the same problem?