Keep getting: Oops! Firefox could not connect to

When I try to access several pages I know are working I am getting that message

Oops! Firefox could not connect to

Anyone else having this problem? Its doing it in both FF and IE

it seems to be there are other people who have this exact same problem in FF, IE & Chrome as well: but i can't find any solution while reading
it's kinda weird, this problem started not too long ago (sometime in April) as you can see it from the search results and it's even more weird that it's not browser specific, so it can't be a bug in the new versions, it's something else :dontknow:

weird...here i didn't get anything...but this things happens when you have some dns server problem in your ISP, or soem DNS server is down between you and the page you're trying to acess

I have had this problem using the Fiddler add-on for both IE and FF.

I don't know if you have it or not, but if you do, I'd suggest uninstalling it.

Yea I get this mainly on my office pc but I get this at least once a day