While generating a new profile or adding sb to your friend list, the Wii sends the record "getprofile" to the server (containing a profile id) and the server answers with some information data about this profile (pid, nick, userid, email, lastname, lat, lon, loc) and also a checksum string "sig". The Wii doesn't accept packets with a wrong "sig" parameter so we need to find out how this is calculated.

@Chadderz: Are you able to find out where this checksum (it's an MD5 hash of something) is generated in the game and which data is used for this hash?

Leseratte

OK, the parameter sig isn't needed, there was a mistake in the database that disconnects the wii. It now connects fine without the right "sig" parameter (but games still don't work).