Mac OS X american channels are not working

hi there,
i just installed the supertv addon but couldnt get the american channels running at all. all others i tried(german/british) worked well but unfortunately americans wont. whats my mistake?

thanks

btw: the wheel at the down right corne starts spinning and says working but after a few seconds it disappears again and nothing happens =(

PLEASE any ideas? the channel selection is awesome but none of them is working=(