I have two laptops at work, both connected to the same network. One is quite happily connecting to Stack Overflow, the other gets 403 (unauthorised? Can't be bothered to check).

The main differences between the two laptops are:

Working laptop: Vista, proxy IP Non-working: XP, proxy IP

The non-working laptop also routinely runs fiddler, but the fault happens with or without fiddler, on all the browsers installed, and continues to fail even though I've cleared cookies / cache. The only thing I can assume is that the proxy's IP has been banned. This affects most of the Stack Overflow family, including meta, and superuser.com.

What did I do?

  • 5
    Create another account to upvote your posts. Maybe that's it. – random Feb 2 '10 at 9:39
  • I have seen strange issues with Fiddler before, similar to yours. Try to uninstall Fiddler just to be sure. Also, have you tried another browser? – Magnus Feb 2 '10 at 9:55
  • Ask 'n' number of Subjective questions... – ACP Feb 2 '10 at 9:56
  • 2
    Well, if I had been vote rigging, I've been pretty bad at it. Sadly I cannae uninstall fiddler, it's more useful to me than stackoverflow is. But as I didn't used to get the issue with fiddler, and I get it even when fiddler's not in use, it seems unlikely to be the cause anyway. I'll give it a go though, but if that's the solution, then no more SO for me. Sigh... – Massif Feb 2 '10 at 10:48
  • @random: I'm confused.. how do you know he's upvoting his own posts? Did I miss something? – Thomas Bonini Feb 2 '10 at 15:08

Swap the machine/proxy assignments to see if it's a problem with the machine, or the proxy.

If it's the machines, then you'll have some difficulty tracking it down, but since you can see the HTTP requests using fiddler you should be able to see what the difference is in the requests that causes the site to spit you out.

If it's the proxy, check to see if both proxies are configured identically. If not, swap the IPs on the proxies to find out if it's a problem with the IP or the proxy configuration. Pay attention to the HTTP request to see if perhaps one proxy is giving you the 403, rather than the site itself - could be blocked at the proxy.

If it's the IP, and nothing else is different, then email team@stackoverflow and request their assistance in determining if they have that IP blacklisted.

If at any time in the past your computers abused SO (lots of traffic, bot, etc) then you may have fallen victim to such an IP block that usually automatically clears. Are there others using the proxy? Could be them. Either way, if you're certain it's the IP then email the team and ask if they can give you an idea why this might be happening. They won't spend much time on the issue, so don't expect a thorough examination, especially if you haven't done most of the investigation already, but they are usually good about answering simple requests.


Maybe it's your proxy?
It's the first thing I'd check...

(It's obviously a problem at your end, not much they can do from here)

  • 9
    You could try a few human sacrifices, but that's your call – juan Feb 2 '10 at 12:53

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