My Win7 computer periodically loses network connectivity. This occurs from every five minutes to once or twice a day. The troubleshooting option of the Network icon in the System area goes through the process and then the problem is fixed - until the next time. The problem is listed as "Default gateway not available." with the notation "Fixed". I have Googled this and found many others with the same problem, but nobody has suggested a fix that works for me.
I am using the latest drivers for my motherboard Realtek PCIe GBE Family Controller. This computer is connected by cable to my router (Linksys WRT54G). All other non-Win7 computers, wireless and wired, remain on the network.