I figured out my problem, it was my fault. The auto conversion needs to be set to M4A rather than AAC.
martialartsguy probably has a different problem.

I am running into the same problem. My iPod Classic 80GB crashes/reboots when trying to play any song after syncing with MM4. Yesterday, after installing MM4 and the Codec Pack for the first time, I reformatted my iPod Classic. Then I synced, which automatically converts FLAC to AAC. The song names ...