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I'm using Windows 7 64-bit and Ubuntu . My hosts file is empty. I'm using Firefox and Internet Explorer.

When I tried to visit some sites I get a Server Not Found error. If I refresh the page a few times, it's working.

However some sites (for example cloudfront.net) aren't working outright.

I have also tried it with OpenDNS with the same result, and on two different locations.

What do you think the problem might be, and how could I fix it?

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Under Windows, check the event logs using Event Viewer. Under the DNS-Client, it should say the DNS query timed out if it is a DNS problem.If it isn't a DNS problem, then you'll need to run some more tests the next time this happens.

The next time it happens, you'll need to use nslookup to send a DNS query. Narrow down the causes. Without more information, we might as well be sifting through a haystack . . .

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Hello,There isn't any error for DNS-Client . This is the result of nslookup: Varsay²lan Sunucu Address: 8.8.8.8 – Eray Oct 30 '11 at 21:24
    
If the DNS resolver is getting an IP address, but the server behind the IP address doesn't respond, there is little you can do in that case. – surfasb Nov 1 '11 at 13:51

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