New computer - iTunes not allowing manual syncing of new songs onto iPod

Recently, my computer died. Fortunately, I was able to save the content of my iTunes. I loaded it all onto my new computer and decided to add on some new songs as well. I then plugged in my iPod, which appeared in iTunes, and found that it would not sync with the iTunes. I tried to put the new songs on manually, but it freezes up and will not do anything. What do I do?