Are you certain that you did not place the wrong album art by error in some songs?

And that also makes me wonder if you are adding album art for each song individually... if so, you could actually select all tracks of a single album, get info, and add the single image file to the image art box and it will end up with all tracks.

In that case, connect the iPod to the Mini, delete the library from iPod and resynch... depending on the size of your library, it might take a little time but it's hands off time. I am not certain why or more to the point, how the problem came about but reloading a good library ought to fix it.

I am assuming that your iPod software/firmware is all current!

How about running Disk Utility on iPod... I imagine that one might be able to zero all data via Disk Utilty as if it was an ordinary FW drive and then initialize the iPod through its built-in system... I imagine, it would come up with an empty library at that point, which is fine but perhaps all the bad blocks would haev been remapped, should that be the case and cause of corruption of addresses. But be warned that I have never done it and it is all a conjecture.

I have had iPod since the generation 2 version and a couple more since then and a variety of computers that support iPod but I've never encountered the problem you are describing where everything seems fine on the computer but on iPod things are whacked. Since I tend to draw primarily from my own experience, I'm afraid that I wouldn't be of any further use in assisting you... perhaps someone with more experience with iPods might be helpful. but in the mean time, try a few general searches via google and also read iPod related posts on Apple boards.

Good luck and sorry that I couldn't help.