I'm not sure if it's a font cache issue, but I've found FontFinagler to be a kind and apt font cache cleanup app.
This doesn't look like an instance of corrupted font caches, but I'm not one to disregard anything when it comes to fonts. This used to be a problem with 10.3, but I've noticed it a couple of times with iTunes...
Anyroad, here's more on font problems. Fixes are at the bottom. Again, I don't think this is your problem -- if you have a font cache issue, it usually manifests itself in more programs than just one and also shows up as random symbols.
I've done all of these steps above and the problem seemed to go away... until it came right back again a couple of hours later.
A quick fix for people with this problem: when it happens, switch to the 'iTunes Store' then back again to your library. This fixes it on my iMac (obviously only temporarily)
Found mentioning of a quick fix on another site: Just enter iTMS and then it should redraw the headers once you go back to your own library/playlists...