It happens on almost every website. For example, sometimes even google.com and facebok.com won't load after multiple refreshes. And it's been like that on both home and office networks.
Nothing has changed as far as connections really, still the same networks at work and home, this just started happening 2 days ago.
Have you installed something recently that might be interfering with web activity? Maybe there's a corrupted file? I'm thinking of Click-to-Flash or something like that.
I agree with the others about it being a connection issue, but rarely does speed cause the problem you're seeing. It is more likely packet loss or something along those lines than actual speed.
Do a ping on your router, let it go for a while (30 seconds or so) then see how many packets are lost (local test).
Do a ping on google.com, let it go for a while then see how many packets are lost (remote test).