In all my years working with Windows I think this is the strangest networking problem I've seen. As of yesterday I noticed that one of my Windows 7 64 machines on my home network (wired) would not load certain websites, most noticeably Wikipedia. Now, I cannot access Wikipedia on this machine by the usual web address OR the ip address, for example http://208.80.152.2/ does not load (it should bring back a "Wiki does not exist" page). Here's what I've tried Other PC's on the same home network connect to the site just fine. I can ping and traceroute to 208.80.152.2 just fine on the problem machine I cannot connect to the site using Firefox or Internet Explorer I have tried two different DNS servers, same problem Checked hosts file, it is the default I've cleared the ARP cache I've reset Winsock I've uninstalled and reinstalled the LAN adaptor Full virus scan shows nothing Completely disabled Windows firewall and my antivirus I used a UBUNTU VIRTUAL MACHINE running on the problem machine with the network card settings set to NAT and THAT wouldn't connect to Wikipedia either (BUT it would if it was set to bridged network) Utterly baffled at this point, I've got heaps of software installed on this machine so reinstalling really is a hassle I could do without, any suggestions would be welcome.

Well well, looks like I figured this out myself, though the answer surprises me. A week or so ago I enabled Explicit Congestion Notification ( netsh interface tcp set global ecncapability=enabled ) because the Internet Connectivity Evaluation Tool said that my system was compatible. I don't know why but when this is enabled, certain websites simply will no longer load. Let this be a warning to anyone who tinkers with this setting! If anyone more knowledgeable than me can explain why this would happen I'd be curious to hear.

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