Might be worth googling Nat table overflow. Not sure if Englishmans issue is that. need to know the make of the Device and the components plus whats actually runing on the Windows 7?
Powersaving, network cards chipsets and routers not agreeing plus the software to create the network connection on your laptop are prime candidates.. But sound like your troubleshooting has elimated a lot of this..
Im using windows 7 x64 on a dell with a billion router and touch wood it hardly ever drops out.
Any peer to peer applications running including skype and torrents but other applications use peer to peer connections? Plus how many connections are open on applications and browser on avearage? Some routers simply can't keep up with the data it needs to thoughput and process...
Not sure on a small network people worry so much on firewalls on the devices i prefer to use the routers and if need be a device (PC or standalone device) behind the router running as a firewall.
Make sure if using Smartphones and Tablets smaller netbooks you have a decent Firewall running on your router or just behind it..
