Recently I noticed Firefox was acting rather slowly. Navigating to any page would seem like a chore and I could see the message in the status bar that Firefox was busy spending its time trying to lookup the domain name. At first I thought it was my university’s network, it has gone wonky before, but that was usually only for a few hours at most. Also no one else seemed to have the problem.
Even just recently updated to Firefox 7 and still was slow going. So I go and google my problem and lo and behold a solution. Firefox was busy trying ipv6 dns lookups everytime. So go into about:config, search for network,dns and set network.dns.disableIPv6 to True. Problem solved.