Oh good. I was afraid this was just me. I too have to power cycle repeatedly. I don't think it has anything to do with inactivity, though; I frequently see the wireless connection go dead while I'm in the middle of doing something online (e.g., watching a streaming video, which is about as non-idle as you can get.) This happens to all my devices: two MacBook Pros, a ThinkPad, a Wii, a wireless webcam, etc.
Wired connections are not affected. The router seems to be able to get to the Internet just fine; it's just the wireless that drops out.
When I look at the TCP/IP settings on the computers after they lose connectivity, I see they no longer have IP addresses. And if I reset one of the computers' wireless interfaces, the router never assigns it an IP address. So maybe it has something to do with DHCP lease renewal? My lease period is set to several days.
The only suspicious thing I see in my logs is the following, which happens a LOT (hundreds of times a day):
Wireless system with Mac address 00:22:b0:c6:b4:61 deauthenticate reason 7
That is the router's own MAC address, which is strange; why is it trying to connect to itself?
Hardware revision C1, firmware 3.01.