Same problem
What router are you using?
I didn't notice it was crashing the router first off and so originally though it was a problem with Windows 7, possibly driver problems.
I'd originally been using Win7 through a virtual machine and didn't have any problems at all, however when I did a fresh install of Win7 and started using that I immediately had problems.
I first noticed it with MSN Messenger, I couldn't stay online at all. It would constantly reconnect.
I thought I resolved it by switching messenger programs to pidgin but finally realized the router was crashing when I noticed I was being disconnected in other things as well. I checked the router logs and sure enough the router was crashing.
I actually had other routers I could try so I replaced my original linksys BEFSR41 with another linksys, model BEFSX41 both are older models and most recent firmware for them are 2 or 3 years old. Same problem though.
I have since put in a Dlink 704P, which is also an older model router but, fingers crossed, I've had no problems for 10 or 15 minutes now, which is a Major improvement because with the linksys if I logged in to MSN it would be down in less then a minute.
You running on a linksys as well?