In reply to Jimbo W:
> The tracks are listed in the ipod fine, but clicking them doesn't play them,
That suggests an encoding problem... Possibly in the MP4 container format (media generally has two formats; the codec format, and the container format that holds the codec data, and has information on the codec type, bit rate, etc). In this case, MP4 (MPEG-4) is the container format, and ALAC is the codec format.
You can pull the tracks back off the iPod using MM:
Select iThing in LH browser
Select 'Music'
select all music you wish to copy
right-click 'Auto-organise'
select 'copy files to new destination'
specify destination format:
e.g. E:/iPod/<Album Artist>/<Album>/<Track#:2> <Track>
untick the 'Add copied files to the Library' option
click 'OK'
off it goes...
Select a single album, and then see if you can play it under MM.
Or, try converting to ALAC locally (to a parallel directory), and then syncing the file to the iPod, and seeing if it will play.