I use a proxy server. When I manually configure the proxy settings it does not work and give the error message as "can not connect to proxy server." But instead when I keep proxy setting as 'use system proxy settings' then it works fine But it causes other problems. I want that it work with manual proxy settings. P.S.: Using no proxy is not a solution for me. Please do not suggest me the same.
Please try updating Firefox to the latest. You can then Reset Firefox via Help (Alt + H) > Troubleshooting Information. If the problem persists, please also try to Import data from another browser via Firefox Bookmarks (Alt + B) > Show All Bookmarks > Import and Export. Choose Internet Explorer, and Internet Options in the next screen.
(To revert to the previous profile you were using, close the new profile (i.e. exit Firefox), start Firefox and choose the Default User profile. While the Profile Manager is open, you can also delete the newly reset profile (the one containing random numbers), or the former profile, as the case may be). If the reset is okay, it would be a good idea to delete the old profile as otherwise it would be left intact with the previous data/cache until deleted.
Import data from another browser usually is the same as using system settings. Can you please create a screenshot of the error page you're seeing by following the guide mentioned at How do I create a screenshot of my problem?.
Once you've done this, attach the saved screenshot file to your forum post by clicking the Browse... button below the Post your reply box. You really help us to visualize the problem.
Here is the error report I am getting. I am also attaching the proxy settings which I am using. The same proxy settings I used before also and they were working fine. But since last 20 days it is creating problem.
Well actually that was, you have to set the SOCKS Host, and also network.proxy.socks_remote_dns to true. Sorry about that. If it's still not working a good start would be to check with the network admin regarding the type of proxy. You can also try to copy the Internet Explorer settings from Internet Options > Connections > Lan Settings.
Actually I verified that with the same settings my friends are comfortably using it. They are not facing any problems. That means it is not a problem from administrator's side. Even I used the same settings. I did not face the problem earlier. I also formatted my computer and reinstalled everything. I tried all the ways you suggested but still not getting fixed. I think I have the only option to use another browser.