Computer not authorized to play certain songs??

Ever since upgrading to the latest iTunes, something weird has been happening. Certain songs within my library won't play and a pop-up window appears asking for authorization, saying "this computer is not authorized to play this song" showing me a username and password box to enter info into. When I enter my account info, nothing seems to happen. Never beore has this happened to me and I don't know how to fix it. Anybody have the same issue or know how to solve this issue?