Cannot access certain websites on any web browser

What browser are you using? Have you tried using OpenDNS servers? Reinstalling an entire OS for your issue is overkill and not necessary because it is not an OS issue.

Try a different user on the Mini, or a test user, to see if the problem only happens within your account. If it happens in both accounts, you've probably got something in the root Library causing trouble.

I have this problem as well. K.panic, what would the troubleshooting steps be to find the root Library problem?

Same for me, started with Facebook on all browsers (FF, Chrome, Safari)a month or two from now, and today twitter and this very support.apple.com + some software like ClamXav cannot connect anymore to update their database, etc.
In VirtualBox with Ubuntu and VMWare Fusion Win XP : both with FF, same problem, same websites / IP

_It is neither the router nor the DNS_ since my wife's computer works fine on the same network with all those websites and apps (PowerPC 10.5.8)
_It is not the firewall either_ on or off, it does not change a thing.

So far, I managed to make it all work (even apps like ClamXav) by using Vidalia TOR + Tor add-on on FF || Tor Browser (Safari under Namaroka) works great too.
Tor makes browsing a little bit slower and anonymity can have its drawbacks, so it is not a long-term solution.

So for those in need of a quick access to their websites :
www.torproject.org > Download > Tor Browser Bundle for OS X Intel

Now, why is that it works with Tor and not without ?
What to do to solve the situation ?

TIA for any help !
--
Jc.

I am having the same exact problem. I can ping twitter.com and apple.com but I cannot load them in ANY browser.

Not a firewall issue

@k.panic : all user accounts on the same computer are affected. Then what kind of root Lib problem shall it be ? How to locate it ?

@beantown696969 : I confirm : Ping works, not browsing

i got twitter to work in safari by making an exception in the proxy for twitter.com

i'm going to bring it to the apple store today

@k.panic it is not specific to the user, it is happening on all user accounts

I have the exact same problem with twitter.com can't connect to it no matter what I do using my MBP. Browser choice and DNS server make no difference. I can get straight on via my iPhone (which is connected to exactly the same network)

Checked my hosts list and proxy settings, can't see anything amiss. Anyone have more info on this issue?

Do you guys have PeerGuardian? Deleted that and it fixed the problem.

I am having the exact same issues with Apple.com and Twitter.com. Changing DNS to Google's or OpenDNS fixes issues with Apple.com (although I'm still not sure why the problem started in the first place with my ISP's DNS), but I still cannot access Twitter from ANY browser. Changing DNS does not fix the problem. The guy at the Apple store told me to reinstall my OS, which I did and that did not help. This is very annoying.

@beantown : I agree, PeerGuardian is at the root of the problem. If its lists are disable everything return to normal.

Quesiton is : how is that PeerGuardian interfere if the application is not even launched, not even as a process ?

did you try chrome? if you can't access it with chrome, then its being blocked by your ISP

Chrome is my default browser.

After disabling all filters in peergaurdian I am able to access twitter.com and apple.com, etc. So it appears that PG is the issue. I didn't think it was because PG was not running, and I have a script that runs during bootup to kill all PG associated processes running in the background. But still it was preventing these sites from loading (woot.com was another one I discovered today). So I suppose uninstalling PG is the best solution, unless someone knows how to add exceptions....?