OSStatus error -50

I am trying to recover from an incorrect attempt to upgrade directly from Snow Leopard to Mavericks. I have re-installed Snow Leopard and restored from Time Machine. Unfortunately, Time Machine restored the kinked post-Mavericks-attempt version of my system and that has left problems. I can view videos with Quicktime but cannot save them with different names—even after Trimming. Quicktime 7 (which I keep for older files) won't even open some videos. I'm getting an "OSStatus error -50." Any ideas?