HTTP transfers failing due to OS X user profile problem

[arogge]

I have a new networking problem that is driving me crazy. Last week, I suddenly started having problems accessing a specific domain name. I haven't changed anything about my network settings or installed anything on my Mac that has the problem.

For some unknown reason, when I try to access anything on http://<Domain>, I can only get about a megabyte of data through to my end before I am totally locked out. My browsers insist that the server has closed the connection, and this lockout lasts approximately three minutes. Then the domain name becomes accessible again, until I try to transfer more data, and then I'm locked out again.

Here's what I've found out so far:

When I am locked out, the lockout extends to everyone on my network segment. It's as if something is flooding the network with bad requests, like a Denial of Service attack.
Once the lockout is released, other local machines and other Mac OS X profiles on the same machine and using the same browser software have no problems accessing the Website in question.
While the lockout is happening, I can access pop.<Domain> (e-mail) and ftp.<Domain>. I can also ping the domain name successfully, but anything related to HTTP transfers to this domain remains locked out for approximately three minutes.
This problem is specific to this domain name only. I can access other Websites without problems while this lockout is happening.


Does anyone have any suggestions for what could possibly be causing this problem? I am at wits end! I've been blaming everybody else for two days, and am now very embarrassed that the problem appears to be somewhere in my own OS X user profile.

 

[belvdr]

What if one of the other machines accesses this data? Does the lockout occur then?

 

[arogge]

What if one of the other machines accesses this data? Does the lockout occur then?

Other local machines have no such problems, and other OS X profiles on the same machine with the problem don't have the problem. Additionally, Opera 10 was working under the failing OS X profile, until I signed into the domain in question through HTTP authentication. Then, even if I sign out of the site, Opera consistently has the problem under this OS X profile.

Safari, which has never been authenticated with the Website, does not have the problem. The problem isn't even global within the OS X profile that has the problem. I authenticated with Opera on another OS X profile and the problem did not occur. There is something between the HTTP authentication of a browser and this domain, and only within my regular OS X user profile.

What is really strange is that the one domain access that is failing is the same domain that I own and which have been working on for the past few months, and that's too strange to be a coincidence.

 

[arogge]

I've narrowed down the problem to something that affects only two browsers, including a newly-installed Opera 10, on one OS X user profile. Safari and Camino do not have the problem, logged in with authentication or not on this user profile. What am I missing? What can damage the networking functionality of two browsers that isn't global at the system level or at the user level? I'm thinking that it must be something that I did last week, but I don't know what that could be, especially since I wasn't even using Opera last week.

I remember when Folding@home used to do something similar. Unable to connect to the work-unit server, it would occasionally flood my network with bad requests, but it would slow down all Internet traffic. This is specific only to one domain, two browsers, and only one OS X user profile.