iOS 4.1 iPhone bug (iPod related)

For some reason, all the artists with names beginning with J and K are appearing under the "K" section of the iPod (you know when you scroll down through the artists, they are all broken up by a little blue banner with the letters of the alphabet on them that separate the artists by alphabetical order.

It goes straight from I to K, and misses out J, with all the "J" artists being in the K section.

Any ideas what I can do to fix this?