I did a fresh install of Vista and had the problem still. Here is what I found out.
The reason this is, is because of the way Vista displays thumbnails.
Something I think that wasn't in XP, is that Vista detects if the start of the video is a fade-in and only shows the thumbnail of the content after that fade-in, because if you had a folder full of files that started with a fade-in, all you'd get would be blank thumbnails.
So Vista goes through each frame to find the lightest. If Vista finds one that is light enough within 7 seconds, it displays, otherwise, it times outs.
Because that puddle one is dark the whole way through, Vista goes through EVERY frame to find the lightest, because the lightest is quite near the end (those who are seeing the thumbnail will see it's near the end) the request will probably time out for most machines.
So the faster computers will be able to display that thumbnail, slower ones won't. However, if Vista grabs it once, it'll be cached.
