WoW has a spam filter if you flood a channel with messages you'll be disconnected. This happens with any of the channels, including the addon only and hidden channels. So it is quite possible for an addon to cause a disconnection problem. Completely killing the router is a different thing though.
Jamba has disconnected me when I mistakenly spammed the heck out of the update FTL macro in the Jambadev version. I've also had it happen with a quest sharing addon (can't for the life of me remeber what it was called) that didn't throttle the shares.

BTW what is it you did in vista to diable the router sleep and large packet problem? I've been looking for a way to do that for a while.