I changed my port and it had no effect.
I DL'd Acquisition and I get the same results with that program... up to 5.6kb/s speed.

I don't see how my Cebridge Cable connection could be the problem, since it initially gave me DL speeds that used the full bandwidth (close to 512kb/s). Something has changed though. I'm trying to figure out if enabling Apple's built-in Firewall has done something, even though I have had it disabled for a week.