General :: Google Music Won't Upload Whole Library?

I've been trying to upload my music to Google Music, and I ran into an issue yesterday when I saw that it stopped uploading. I had it running for about a week and I have roughly 3700 songs on my computer (in iTunes). It stopped at around 2400 songs and won't add anymore, and I'm not entirely sure why. Of those 3700 songs, only about 300 were purchased from iTunes, the rest are CDs or songs that I permanenly borrowed during the Napster days. I double checked the songs that are missing, and there really isn't too much rhyme or reason as to why they're not there.