Here is what you should do.
- Open Firefox and type
about:configin address bar, hit enter.
- Scroll down until you see a line like this
network.dns.disableIPv6 = false
- Double click on this line so that it becomes
network.dns.disableIPv6 = true
PS: This is the solution that worked on my machine. There might be other issues related to network that might cause page load latency. This is just one of the solutions.