Drupal | Flashvideo thumbnail problems?
Search no more, Travis gives you the fix:
The only anomaly has to do with CCK's weight is higher than that of the FlashVideo's weight which will ignore the tags [thumbnail] and [video].
However, you can fix this fairly easily by just changing the weight of the FlashVideo module (in the system table of your database) back to 10.
Tried it. Works. Yay.