I have four computers in a local wired/wireless network, and one of them suddenly lost Internet connectivity yesterday. All of the other computers are connected to the same router and have no problems. The three others can connect to the faulty one's web server as well as remote desktop into it, and the faulty computer can connect to the other three. The faulty computer can ping google.com, etc., as well as resolve domain names. However, if I try to make an actual TCP connection to any Internet-based server (e.g. google.com), it just hangs and times out. It also fails to connect if I use an IP address.
Perhaps the strangest effect is in the Network and Sharing Center view. There is a red "X" between Network and Internet, implying no Internet connectivity. However, when I ping a remote host from the command prompt, the red "X" disappears temporarily, but reappears after a while. I still can't actually connect to anything during this period of pseudo-Internet, unfortunately.
I have tried disabling/enabling the Local Area Connection and uninstalling/reinstalling the ethernet device, and disabling the firewall both in Windows (Vista) and on the router. The problem persists.
Any suggestions on what else I should try?