what does error message (-69) mean?

A corrupted song or songs.

In the course of your troubleshooting to date, have you worked through the following document?

iTunes displays a -69 error when syncing iPod

I wonder if thats the only reason for the error. There doesn't seem to be anything wrong with the files... I can play them just fine, even in iTunes.

They may play in iTunes (your computer has much more processing power) but not be able to be moved/played on the iDevice.