Need to think outside of the devices possibly doesn't sound as if your using any peer to peer connections in software you use. What these can do is keep opening and opening connections untill the routers Nat table is overloaded and crashes. NAT in a nutshell is part of the process in converting your internet connection os it can speak to the outside world and viceversa.
Sometimes when troubleshooting people get to hung up the problems is in a certain area or concentrate on the technical side.
Is there any unique time, place or scenario where you use the win 7 device?
Have you loaded http://www.netstumbler.com/downloads/ and left it running to see if the signal gets interupted or is faint. Just to eliminate a Wifi issue and has MR Boss Admin mentions best to check power settings if you use all over the house garden etc..
Worth setting one of the xp laptops and win 7 in same location away from server with netstumbler running and then seeing what teh results are stength of signal etc..
You mentioned DNS and I know in the past Talk talk and DNS has been a source of peoples pain when web browsing..
Have a look at this http://www.google.co.uk/#sclient=psy...w=1366&bih=599
If your comfortable access your Routers config page and see if using google DNS or one of the other DNS providers ip addresses makes a difference.
As you use Droids i would think you have no problem with using another google product
http://www.youtube.com/watch?v=beTp_YYNOxo
Some ISP's DNS service for some is not as good as others.
At home we usse google DNS and it makes a difference to the speed it takes for pages to be found compared to BT's. Certainly makes a difference not having the router have to ask for settigns from the ISP...
