Hello there NAWS2012,
There are 3 things that I might recommend. The first option is to reinstall iTunes. Not just iTunes but all of its ccomponents as well. Here is an article that will walk through that process.
Removing and reinstalling iTunes, QuickTime, and other software components for Windows Vista or Windows 7
Or you may want to try rebuilding your libray and playlists to see if the issue lies with the iTunes library itself.
iTunes: How to re-create your iTunes library and playlists