how are you connected to the router?
What is your ISP service? Cable or DSL?
What is your ISP modem? Stand alone or built in?
Try setting up reserved IP addresses on the router for your devices?
Wireless and Wired. (different pc's but also tried wired on problem laptop)
Roadrunner(Cable)
Voip cable modem, standalone
Did set up reserved and some out of DHCP range
Its not my setup, its the router/firmware, downgraded back to my WRT54G2 with the exact same settings and haven't had a problem since.
I suppose I'm not new to the whole networking thing, I know the in's and outs of basic networking and have successfully setup many home networks.
I'm hopping this is fixed with future firmware updates, from what I can see is it closes the port for UPnP after so long of data not being sent. I could be wrong with it being the UPnP since even with the ports opened it would still close the connection somehow.