A possible cause is security software (firewall,anti-virus) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

I'm behind ForeFront TMG and have similar issues. I'm wondering (uneducated guess) if there's an issue with proxy authentication?

If I open the Net tab of Firebug, I can watch each individual request start and end in milliseconds, but happen roughly two seconds apart.

With TCPView I can see Firefox produce four or five new UDP processes a second, and close out each one about two seconds after it starts.

WireShark shows aobut 60 UDP proxy-control packets back and forth between every HTTP request, but I don't know how to parse that data.

thanks for the reply.

i tried removing "mozilla firefox" from the firewall's allowed programs list, but when i launch firefox the firewall does not ask for permission.

i also worked through the suggestions in the provided kb links, but still i can not access the external web.

i tried loading a site on my company's INTRAnet and that page does load... which i think further suggests a problem with the proxy.

i tired various proxy settings but that does not solve the problem. currently i have it set just like ie (which always worked in the past).

thanks.

also... my proxy settings are set to "Use system proxy settings"

My proxy is also set to Use system proxy settings.

Disabling the proxy in Firefox resolves the performance issue. our network admins have configured Forefront to proxy all traffic from Firefox. This means we aren't using the authenticated proxy client (e.g. some users have permission to access social media). It's not a long-term solution, though.

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if the "Use the system proxy settings" setting or one of the others doesn't work properly.

See "Firefox connection settings":

• https://support.mozilla.org/kb/Firefox+cannot+load+websites+but+other+programs+can

• Tools > Options > Advanced : Network : Connection > Settings

• https://support.mozilla.org/kb/Options+window+-+Advanced+panel

i have tried all the various options for the proxy settings (except "manual") and still i can not connect to the external web.

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

ufortunately SafeMode does not appear to be easy with bitlocker enabled... i'll let you know if i can figure out how to test this.

Do you have any proxy related add-ons in Firefox?

Hi, same problem here behind proxy with authentication (ntlm) Tried both: - Plain vanilla firefox 18 installation - Upgrade from firefox 17

Result: firefox keeps asking for authentication credentials again and again and cannot connect to internet.

Solution: rollback to firefox 17

Regards

Ok so this looks like a bug in Firefox 18 which will be fixed in Firefox 18.0.1. Expect this release sometime next week. In the meantime keep using Firefox 17.0.1

Everyone who is afflicted by this problem, please go back to Firefox 17.0.1.

There is definitely a bug with proxy component of Firefox.

For the time being, I would advise everyone to go back to Firefox 17.0.1 until Mozilla fixes this bug.

Actually, please only downgrade to Firefox 17.0.1 if you are using a proxy and Firefox won't connect over that proxy. Otherwise please don't downgrade to 17.0.1 as 18 contains about 2 dozen security fixes.

Or, better yet, use the Firefox 17.0.2 ESR, which has the security fixes without the proxy changes. http://www.mozilla.org/en-US/firefox/organizations/all.html

Don't know if this will be fixed in 18.0.1. I tried the 19.0b1 Beta, and the issue is still there. Downgrade to 17.0.1 fixed the proxy issue.