Open the folder in question, then RIGHT click on a blank area of the folder, choose "Customize this folder" from the little menu, then click on the "Customize" tab, then use the drop down menu to "Optimize this folder for", select "videos". Select "apply", then OK.
Hope this helps.
Grif
why do i only have icons and not thumbnails of my saved videos? i used to have thumbnails

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic