I recently set up a wireless network for my wife's workplace. They have two Acer Aspire 5349 laptops running Windows 7 SP1, connected to a Linksys E1200 wireless-N router (via Atheros AR5B125 wireless network adapters).
Whenever any of the laptops goes to standby after a period of inactivity, its wireless connection is dropped. After waking up, the laptop displays the connection to the router as live, but the internet connection is shown broken. Disconnecting and reconnecting to the router does not help if the laptop in question is the only active one on the network - in this case, our only known remedy is rebooting the router. If there is another laptop connected and active though, disconnecting and reconnecting to the router solves the problem.
At home we have a similar wireless setup, only with a Linksys WRT54G router, and the problem so far hasn't occurred here. So to me it seems this may be specific to the E1200. Unfortunately Google hasn't turned up any hints.
Both networks have WPA2 AES security and MAC address filtering enabled, and the laptops are set to connect automatically on startup. No Linksys specific applications are installed on any of the laptops, only the standard OS wireless feature is used to connect. The router firmware was updated at the time of the network setup, a few weeks ago. Both laptops are connected to the power plug most of the time.
Any help or hints would be appreciated.