Can't Browse One Specific Site

Never seen this kind of problem before. I am unable to get to usedvictoria.com in Firefox 17 on my iMac OSX 10.7.5. I can browse to any other website except that one. Here is what I have tried:

-pinged site. and checked with other users. It IS up and running.
- tried other browsers: Chrome-No difference. Safari-No difference
- checked Hosts file.
- Repaired permissions.
- Flushed DNS cache.
- tried on MAcBook Pro. Neither Firefox 17 nor Safari worked.
- tried on IPad. Amazingly, it works under Safarai and it works under Firefox, but only on the iPad (not the desktop and not the laptop). Sheesh.

Any suggestions appreciated!

Can't Browse One Specific Site

Many thanks, logana. Best of the Season to you.

Couldn't be ISP problem, because my iPad connects to the site without a problem over the same Network using the same modem.

DNS? Tried flushing the DNS cache. No difference.

Any other suggestions welcome.

Can't Browse One Specific Site

Thanks, wrldwzrd89. Best of the Season to you.

The hosts file only has the one standard localhost entry in it.

AdBlock Plus is in Firefox but I've disabled it.

SOLVED - Can't Browse One Specific Site

wrldwzrd89 was quite right. Overaggressive ad filter s/w was the culprit. In this case it's that $#@!)*% Peerguardian. Forgot that I even had it!

PG is not that easy to remove. For anyone else with this problem, after using something like CleanApp, be sure to go into your Login Items (System Preferences/USers & Groups/Yourname - Login Items Tab.) And remove pploader and ppagent.

Many thanks for the suggestions, guys. Hope this helps someone else.