yes ur pc will have to be on when u use it.
I dont really have any problems with it as such, although the wii seems to be a little tempermantal at connecting sometimes. As for the pc freezing... no not at all, well not for me anyway.
But remember it'll only work with windows xp. So if u have vista i dont think it'll work at all sorry.
call me Aaronbunny!
Wii code: 6993 4542 2457 6182. plz add me Im a wiily gd friend