User Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:22.0) Gecko/20100101 Firefox/22.0 (Beta/Release) Build ID: 20130620122109 Steps to reproduce: Updated a netbook to Firefox 22 (on Ubuntu 12.04.2). The proxy settings are: *Use system proxy settings is selected. Manual proxy configuration IS NOT selected, but has 192.168.1.103 port 3128 entered in for http proxy. Actual results: Firefox gives the "Proxy server is refusing connections" screen with the choice to try again. (There is in fact no proxy at 192.168.1.103 port 3128.) Expected results: Firefox should not use the manual settings, since they are not selected. The system proxy settings are empty so it should connect to sites directly. Once I removed the manual proxy settings, firefox did correctly connect directly to sites on either manual or system proxy mode.

I choose priority "minor" as opposed to "normal" because it's unlikely to effect all that many people, and there's an easy enough fix.

I can confirm this here. I've hit the same bug on two different Ubuntu 12.04 systems, just after the upgrade to Firefox 22. Your workaround (to delete the text from the manual proxy configuration text boxes, then switch back to "system proxy settings") works for me, as does choosing "no proxy." As an extra bit of info: I did a simple network capture of my system while using the "system proxy settings" option; I see some attempted traffic to the settings leftover in my manual configuration (a localhost SOCKS proxy I was previously using SSH-routed traffic, which is not currently configured). So it definitely seems that Firefox is incorrectly trying to use my manual configuration. While I agree that this is fairly minor, it's still a regression. Regressions can and should be tackled quickly. It appears that this regression is quite new, so if we can .