Internet!

Things to check:

First, make sure that your computer still has an IP address you think it has. Run winipcfg and look at the address (and subnet mask) for the Ethernet card. If you are using DHCP your server could be unreachable, and your lease could have expired. If someone else set their machine to your IP address, you might have lost your address when you last rebooted.

Try pinging address 127.0.0.1 If you cannot ping this address, your Ethernet card or your protocol stack has a problem.

Check that your setting for the gateway is, in fact, the inside (LAN) address of the router. Try pinging it manually. If you cannot ping it, you may have a connectivity (cable, hub, port, etc.) problem.

If all of the above work, the problemis not in your machine. Try power-cycling the router. If that does not cure the problem, if there is a cable box, DSL box, or CSU/DSU, power-cycle that, then wait about two minutes, then power-cycle the router.

(Some ISP's, notably cable providers, periodically change the IP address blocks assigned to each of their local areas. In this case your cable modem/DSL may lose sync, and a reboot of that box restores sync. If your router was getting an IP address using DHCP, a reboot of the router forces it to refresh its address or get a new one.)

Good luck.

I am not going to ad to the fine answer already given other than suggest you scan for a Virus/Worm , that can act in the manner you have discribbed, resetting the protocol , also I would start logging for a while as this also can be a cyber Peeping Tom , that has left a calling card, if you find an abnormality , I would report it. Luck

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