Yeah; you should be able to watch youtube.
However, several websites wields the power of the latest flash players and therefore, you cannot play it until wii sends out an update for the Wii.
There are still a lot of website which offers flash stream videos that are not up-to-date.
There might be something wrong with your internet, or your channel.
I say re-download the channel (for free since u bought it already)
and update your Wii