Yeah i have that problem too with...cough cough...a certain season premiere.
It's not like i'm a complete novice either so please don't think i maybe unclear about the existence of DivX codecs or the player or that i havent tried downloading VLC player as suggested.
Despite having spent an entire sunday looking for the codec required to play it, I have not been successful in finding one which has had any effect.
G-spot names the codec needed to be
'Motion JPEG including Huffman Tables' yet tells me i have codecs installed which claim to be able to procces this format.
All websites i checked gave me links only to the IBM site which didnt enable me to download it either.
Basically i have tried every player and every codec package i've been able to find. I have also tried downloading different versions of these videos but none of them seem to work. HELP!