Unable to access certain websites: "destination host unreachable"?

[sb3700]

Whenever I try to access http://www.dlink.com (or subdomains), or http://www.dzone.com, I get a "Connection closed by remote server" error in Opera (similar messages in other browsers).

When I try to ping or tracert either of the hosts, I get a "Destination host unreachable" error.

This has also occurred on other websites, which I cannot remember right now, and occurs with both Optus (my ISP) and OpenDNS as dns servers.

It also seems to be intermittent. Yesterday, I was able to access http://www.dzone.com without any issues for some time, yet today and the day before, this error was occurring.

Also, possibly unrelated, the website http://www.tv.com is extremely slow when loading.

Does anyone have any ideas as to what the issue is?

EDIT: http://www.opera.com, and link.opera.com are also inaccessible

[sb3700]

Ignore double post, please.

[YoshiMon]

When you are having this problem can you resolve the hosts using something like: http://network-tools.com/

And then go to the IPs directly from your browser?

[sb3700]

The traceroute and ping work fine from network-tools.com, so it must be something from my end.

The IP's are resolved correctly (when I ping or tracert, the IP shown is correct according to OpenDNS's cache). However, when typing either the hostname or the IP in the address bar, I still get the error.

Thanks for reply.

EDIT: Along those lines, a ping from my router is "successful", ie: in firmware, there is an option to ping hosts, and this returns successful. Also, all firewalls are disabled.

EDIT again: http://www.dictionary.com does not work, but the basically aliased http://dictionary.reference.com/ does. However most of the images in http://dictionary.reference.com are served from http://sp.ask.com/ which doesn't load, whereas http://ask.com does. Very weird... :-[

[YeOldeStonecat]

Is your PC free from malware? Lots of spyware trojans now mess with your TCP stack/winsock files....doing DNS redirects to their add servers. Try scanning your PC with several quality anti ad/spyware programs and antivirus, and run a TCP/Winsock repair utility.

[reizel]

try to use antimalwares.. run Malwarebytes...

[sb3700]

Just an update.

I formatted my computer (it was due for a long time...) and this resolved the problem. I never found the actual cause though. My computer was completely free of viruses and malware though (according to AVG free, Spybot, Spyware Terminator, and SuperAntiSpyware).

Thanks anyway.