Syncing Help!

Whenever I try to sync my iPod touch, it just says "The iPod "Emma's Touch" cannot be synced. The required disk cannot be found.", and then followed by a second banner that says "iTunes cannot sync apps to the iPod "Emma's Touch" because the apps installed on the iPod cannot be determined." Please help? I just want to download a couple of apps and a few podcasts! I have no idea how this happened!