Running behind a proxy server
I'm using a proxy server. Why can't I see anything beyond the proxy server with PingPlotter?
If your internet connection is being shared through a traditional proxy server (which is becoming less and less popular since the advent of NAT), then PingPlotter isn't able to use the proxy server to issue ICMP requests.
Current proxy servers almost always run in conjunction with a firewall. This firewall might be set up to allow or block access to ICMP echo requests. If you're using a proxy server and PingPlotter doesn't work against any external sites, then you might contact your network administrator to see if there's a way to get this to work.
If you're using a proxy server in conjunction with NAT or a firewall, then it is possible that you can get PingPlotter working with this. Most NAT servers / appliances and firewalls can be configured to work with ICMP echo requests. You might need to change a setting to have this work, though. Try consulting your firewall / NAT server's manual for details on this.
If your only mechanism to connect to the internet (via any protocol) is via a proxy server, then PingPlotter won't work through this. If you're using a hybrid setup (where your HTTP goes through a proxy server, but other protocols go through some other kind of router), then it's possible you can make PingPlotter work by configuring that router to pass through ICMP echo requests. Your network administrators should be able to help with this.