iOs is not updating on my iPod Touch - how can I fix it? I have an iPod touch (8gb) which currently has iOS 4.2.1.  I thought the latest version was 4.3, but it's not upgrading.  When I go to iTunes, I click on 'Check for update' and it says I have the latest version.

Am I doing something wrong, or is the new version just not available for my iPod?
iOS 4.2.1 is the latest available version for 2G iPod Touches.