Is it possible that your network just dropped the connection (DLink anyone?)
or maybe someone else in the game got dropped..
im not sure exactly how the connection works for BW.. but its probably not the game..
I have a DLink router and it drops the Wii connection about every half hour, it also loses my laptop connection all the time but the wired PCs work fine.
My guess would be a bad wireless router or something causing interference to the wireless connection rather than the game or the Wii being at fault.