Ever since the last update, most of the songs I have purchased through iTunes will either not play, but show the pause icon is available, or it will show a different album art for a song. Help?

Ever since the last update, most of the songs I have purchased through iTunes will either not play, but show the pause icon is available, or it will show a different album art for a song. Help? I have the latest generation of iPod touch that did not have a camera. I think it is either a generation 3 or 4.

I have already restored from a back-up, but the back-up was from the day before. The problem had already been going on for at least a week by then. Tonight I deleted the songs off the unit and then recopied them and still having songs not playing, or playing a different song than the one displayed. Not sure what else to do at this point???