iTunes to iPod sync issues

I have a newer computer and a newer iPod touch. I added new music to iTunes but could not get it to sync with the iPod. The solution reached after speaking with support was to restore the iPod and reload my entire library (7887 songs) from scratch. Hours later, I find that a large percentage of songs are listed on the iPod, but are greyed out and unplayable.

Any idea what is going on?