Weird iTunes 10.6.3 missing album artwork issue

I upgraded to iTunes 10.6.3 yesterday, and I had to restart my Mac for an unrelated issue. This afternoon, I noticed something really weird- all my "Documentary" movies that I purchased through iTunes Store have lost their artwork previews; meaning, if I click on "Movies" in the Library menu at left, then select the "Documentary" genre, and view the movies under "Grid" mode, none of the movies have any artwork along the left side next to the title. It has ONLY affected the "Documentary" movies, but none of my other genres. In fact, I created a separate sub-category for "Disney Documentaries", and those movies are missing the artwork in "Grid" view as well. If I view all Movies in "List" mode, all the movies have artwork EXCEPT the Documentaries. Interestingly enough- if I select a Documentary movie and type "Cmd+I", then select the "Artwork" tab in the "Information" window. the artwork is still there, it just doesn't show in the "List" or "Grid" view. How can I fix this? I am currently rebuilding the Spotlight Index, I've repaired permissions, and even done a verify/repair with Disk Utility, but nothing has worked so far. I've already checked the "Automatically Download Missing Album Artwork" under Preferences, but that didn't solve the problem either. The movies all play fine otherwise, but this little glitch is frustrating me. Please help!