You have a great router. I have recommended that router to business customers. Its gotta be the computer. When the disconnection takes place, does the whole computer freeze? This would indicate an I/O write error to the HD. If it is just the network going, the card could be bad. You also have a Gigabit network card:
Nvidia nForce 10/100/1000 Mbps Ethernet
Look on NVIDIA's website for a driver update. You've probably already done this.
Check the connection to the Internet. You may have packet loss on the line or a bad connection
Windows Key + R to initiate "Run" dialog box
ping -t google.com
Let this go for about 10 minutes. Hit Ctrl-c. If the result is even 5-10% you have serious connection problems. It should be really less than 5% or 0. In that case it could be the modem or the line definately needs to be checked by the ISP. But you say its only happening on your system? Bad cable?