Oh, sweet broadband!
So, after some googling – and I use that term just because it’s an accepted one – I am back to pre-SP4 speed. The solution involved tweaking one of the incredibly obscure registry keys, and to this point I don’t know what I did intially that could have made SP4 barf this way. But if you ever run into the same problem, edit this key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\Tcp1323Opts
and change the value from 0x3 to 0. People with nothing better to do can read this .
