1) In iTunes , went to File > Export Library... and saved the entire library to an XML file. Quit iTunes .
2) Trashed existing " iTunes 3 Music Library" and " iTunes 3 Music Library.xml" files from ~/Music/iTunes
3) Launched iTunes; chose to import songs manually.
4) Selected iTunes > Preferences... , chose the Advanced tab, and set my iTunes Music Folder to what it used to be. (For me, it was on a secondary HD, and without this step, the process didn´t work.)
5) Selected iTunes > Import... and chose the XML file I had just created in step 1.