Podcasts not syncing correctly

iTunes is telling me that it can't sync my podcasts because my ipod doesn't have the 4Gb of space required.

HOWEVER most of the podcasts are already on my ipod - I can play them from the podcasts icon on the ipod and they come up in the podcasts playlist I have on the device - but they are not showing up on the podcast subdirectory for my ipod touch when viewed in itunes.

Given that there are over 500 podcasts on my ipod touch and thus deleting each one separately is not an option, how can I force iTunes to see what's on the ipod and thus not try to copy the podcasts a second time?

I would restore from backup but itunes is not offering old backups to restore, only ones made today :\ (see other thread).

Please help.