I reinstalled Windows, only to have the problem rear its head again. That's when I noticed the message about Windows automatic updates waiting to be installed which appeared just before my connection went bad.
It appears there is a correlation between automatic updates and my crap connection - when I installed the updates, my connection went back to its former self.
Hopefully this is the answer, because there is an even bigger correlation between my connection dying and me wanting to smash my computer with a sledgehammer.
