Same here. It started happening today when I rebooted my pc and tried to reopen a browser window with a few threads open. It loaded the first couple but now I can only access the site with a VPN. So I assume it's some rate limiting thing. Fun times.
Do you have a static IP address from your IPS or one that changes every so often? Could be that the IP you have been assigned is flagged somehow. You might wanna try unplugging your MODEM (and Router, if you have one) for a few minutes (lets say 10 min to be save) and plugging them back in (first the modem, then the router). Maybe your IPS will issue you a new IP.