It could be that the ICO servers are having issues today (although we haven't heard anything so I'm assuming they're fine.)
If in fact their servers are fine then a "network error" points to something connection-related between you and them.
1. You have checked all of your firewall settings etc. so we can move on from there...
2. Could it be a bad connection between you and your ISP right now? Try running a ping-test from your PC to your ISP's local "gateway" and see if you get abnormally high "latency".
3. You could run a "trace" between your PC and ICO's server in order to see if there is a "bad hop" between you and them.
ie. (Navigate the "command-prompt" by clicking "start" then "run" and then typing "cmd" after which you hit "enter")
c:\tracert 22.214.171.124 <---- (this command will "trace" the route your PC is taking to ICO and let you know if there is currently a problem somewhere along the "route")
some things to try...