[DeepSpace9er]

I have been working on this problem for 3 days and Im about to pull my hair out. Here is the scenario: 3 locations VPNed together via DSL and Adtran Routers. Location 1 is in PA, Location 2 is in Kansas, and Location 3 is Northern PA. Location 1 has no problems and all sites are connected and working fine. Locations 2 and 3 have the same identical problem, but all 3 sites have identical routers with virtually identical configurations.

 The problem is certain PCs can only view certain websites. However, I have hooked up my laptop into the router in location 3 and i can access any website but the local desktops there cannot. With the desktop I can ping the world, the sites that do load, load quickly. I am getting DNS resolution. I have no firewall on. I have run checks for malware. I am an administrator. I have downloaded IE7. I have tried Opera. Built new users. Upgraded to most recent patches (I am running XP Pro.) Checked and doubled checked every conceivable setting on Security profiles and the Router's firewall configuration. I have done this many times and this is the first time I have encountered something this strange. Of the websites I cannot load, I am getting the DNS resolved and redirected. I can ping the websites i cannot access and run a traceroute. I compared settings between the working laptop and the desktops and everything looks the same. Any suggestions?

[achtung]

I had something like this happen before.  I'm not exactly sure what it was, but it was most likely the router.  Whenever the problem occurred I simply reset the router and it worked fine.

[DeepSpace9er]

Believe me thats been done many times, as well as the computer.

[Prophet]

There are several possibilities...

You have angered the internet.
You have run out of mana.
You have not made your sacrifice of virgins this month.
Or there's nothing to be done and it's one of life's big mysteries.

If you ever manage to crack the case, the solution will either be embarrassingly simple, or just plain weird and unexplainable.

[diceman111]

The best solution to this would proberly just be to tell your boss that you are working on it then go home and play FS and hope it solves itself

[Ghostavo]

Clogged tubes.

Always clogged tubes...

[JGZinv]

There are three things I can suggest:

1. Erase as much as you can and start over from scratch.
I'd be looking at the routers too, maybe even flash them.

2. Eliminate possibilities. Start at one end and go to the other
checking things in fine detail eliminating what could be the cause.
Typically you'll figure it out somewhere in there.

3. Find the support forum for those pieces of hardware, and ask around there.
Another good place would be the Broadbandreports.com forum.

Lastly as just a tip, it "is" usually something simple. There have been times
where internet users reported AOL, MSN, and Yahoo blocking other companies
sites... but I think that was resolved. The other thing is something like the security
software (somewhere in-line) could be blocking them based upon settings.

Oh and run FireFox... IE is a pain in the rear. 

[Descenterace]

'Zen and the Art of Fixing Computers'

Someone really should write a book by that title.

Try changing things totally unrelated to the problem. Sometimes, they're not so unrelated after all.

[MP-Ryan]

It would help to know what websites you can't access.

You say you can ping the websites - try using WGet and see if you can retrieve the pages from those desktops.

Furthermore, you said some computers can't, which leads me to assume that others on the same network can (and your laptop would be evidence of this).  In which case, you have one of two possible culprits:
1.  Software configuration on the computers themselves - ESPECIALLY since you said ping and tracert both work, it points to the browser. Like I said, try WGet first.  If you can fetch pages through it, then try Firefox.  The likely culprit is Windows security settings, Windows firewall settings, other software firewall settings, or antivirus settings.  Sounds like the browser is getting blocked, but some traffic isn't.  WGet will give you a better picture of that.
2.  Your router is filtering traffic to specific internal IPs.  This would explain why your laptop can get out, but some desktops can't.  This one is easy to test - unplug a desktop, assign its IP to your laptop, and try the pages again.

All in all, a bizarre problem.

Also...

We need a better description.  How many desktops on site, how many can't access certain webpages, and are the webpages universal to all the problem computers, or does each have its own problematic few?