Ipod Sync Trouble (library on external hard drive)

I recently moved my itunes library to a Lacie external hard drive to save space on my computer. The move was successful as I have been able to get all the music to my ipod, and play it through my computer's itunes application when the Lacie is plugged in.

I have had a problem, though, with ipod syncing. It seems every time I plug in my ipod itunes freezes for a good 2 minutes before displaying that it can't read the device and it must be restored. So when I add new music and want to update my ipod, I have to completely restore to factory settings, which takes a long time since I have 67+ GB of music.

Is there some setting I may have forgotten to engage when I made the move? Or is it possible this might not have anything to do with the hard drive move?

Thanks

Casey