Warning: This problem has been fixed for quite some time now. The proposed solutions will not change much. People who have this problem now, likely have it due to a transparent firewall/proxy. It is recommended you first disable firewalls/proxy/internet security temporarily to test if this eliminates the problem.

About

Since the release of Firefox 3 there have been dramatic improvements made to the networking code to make it a lot faster. However, there have been some problems introduced with this. Many people have noticed that Firefox 3 will terminate connections early and these connections will timeout. The problem is further exacerbated by Firefox 3 using persistent connections. In this situation your browser will be unable to make any new connections, either to that site, or to all sites depending on how many "frozen" connections you have.

This problem has been found on all sorts of installations of Windows XP+ with various extensions and no extensions. When Firefox 3 would lock up, other network applications would still be functioning fine.

Temporary Fix

Since this problem is made really bad with persistent connections we can disable this.

1. Open a new tab, and goto: about:config
2. Do not fear the dragons and click "I'll be careful, I promise!"
3. Search for the value: network.http.keep-alive
4. Right click on this value and click "toggle" to change it to false
5. Then restart Firefox

This means Firefox will no longer use persistent connections, and just opens a new connection per request, and closes them as soon as they are done. This will increase the amount of traffic going through your connection by a small amount.

This will fix your browser from completely hanging for up to 5 minutes or more, although your connections will still pause sometimes, however it does not affect the rest of the browser now! Which is the main thing.

Additionally, all of the pages seem to load a lot faster.

Permanent Fix

Since this seems to point to a problem in the network code, and the problem of connections prematurely ending doesn't stop with this fix, hopefully someone at Mozilla will provide a full fix for this.

Notes

If you are running Windows XP SP2+ you might want to hack your TCPIP.SYS file, to allow your computer to initiate more connections at any one time. For more information on this visit: http://www.lvllord.de/?url=news&lang=en