[stomachmonkey]

Try speedtest.net, run a couple of times using different servers.

My ping to them is roughly half what it was to sourceforge.

Check your TCP settings. Ethernet should be Full Duplex. If it's not you can' transmit/receive (talk/listen) simultaneously.

Meaning if not Full Duplex and the other end is noisy you'll never be able to be heard because you are stuck on receiving.

Have you tried testing with a service like SKYPE? It's VOIP.