Firefox crashed part way through sending this question. Here it is again WIn XP Firefox 33.11. I have two PCs with similar configurations. With PC1 Firefox became very slow to connect to some servers. However IE did not seem to have a problem. The ratio was something like over 100 secs vs 10 seconds or less. All the usual remedies were tried including many hours of virus and malware scans. The only solution was to use IE. However PC2 did not have this problem EXCEPT, now and again it fails to continue to make a connection and issues a message something like "The browser has failed to respond to a request from the server". Perhaps PC1 has a more severe case of this problem.