cant save library

hi i get i message from time to time about - itunes library cant be saved, u dont have authorisation.. anyone know whats that about? and with about 1 month inbetween all my libraries dissapears..and i have to make all new...with hight rating and so on.

i have windows 7 and it started with latest itunes and windows.

http://hem.bredband.net/artdia/itunes.jpg

swedish =)