The dogfood system is now based on the July CTP (it's nearly the same).  Surprisingly, we had to fix the NIC setting on the production dogfood server.  This time we knew where to look when we saw terrible data transfer rates from the server.  Rather than being explicitly set to half duplex, it was set to auto.  However, it fell back to a half duplex setting automatically.  Changing the setting fixed the problem.