1. I presume you have all done basic things like deleting temporary files.

2. One user has just pointed out they resolved the issue by re-setting their modem/router (usually means unplugging it from the wall for one minute)

3. DNS results are often cached on your computer. If your ISP changes the node routing it does not necessarily update your cache.
You can clear the DNS cache by going to your command prompt and typing:

ipconfig /flushdns

and then hit enter

then type exit and hit enter to close the command console