I have found a few threads of people having the same issue although I have seen any clear explanations or solutions, forgive if there is a thread with a solution that I missed.
Has the youtube api recently changed, thus the longtail flv player doesn't seem to play the vids anymore, although the playlist and inital thumbnail show up fine?
Are there any solutions, workarounds or ideas to fix this?
Thanks.

Strange, so it appears to be happening in Safari on the mac (version 4.0.3). I tried the player in a different browser and it works fine.