I have a Linksys WRT54g wireless router. Connected to it wirelessly are a pc with xp, an xbox, and an iphone. My wife just got a laptop (toshiba) with windows 7. Whenever she turns it on and connects to the router (wireless) all other connections drop for a few minutes, then everything finally reconnects.
I have a Sony vaio with windows 7 and it kicks off all other computers on my linksys router and then the vista machine and winxp laptop cannot connect for 5 minutes or more. It also happened when we were visiting and I used a netbook with windows starter, it caused all the other computers to drop.