Audio Format not supported but songs used to work

Hi! So I got a brand new computer a week or two ago, used home sharing to transfer all my music from my old computer to my new computer, and everything seemed okay. However, today I decided to finally sync my iPod to my new iTunes library, and I got an error message for 100 songs saying "the audio format is not supported by the iPod" so the songs can't copy onto my iPod. This makes no sense to me, because the songs were literally on the iPod and able to play fine less than an hour ago, until I wiped everything off my iPod to sync it to the new iTunes. I checked the file format on a few of them, and they're AAC files. Also, I have about 900 songs in my iTunes library, and only 297 of them copied onto my new ipod, and I only got errors for 100 songs, so I just don't know where the rest went. Please help! I want my music back!

Also, none of the songs I had trouble with were downloads or youtube converts. All of them were either from CDs or purchased from the iTunes store and I'm using Windows 8 if that helps. Old youtube converted files kind of just didn't do anything (no error message but not on my iPod either), but files I youtube converted and put into iTunes today worked.

Message was edited by: carchiee