"Road Runner is a joint venture, formed in June of 1988 among the affiliates of Time Warner Inc., MediaOne Group Inc., Microsoft Corp., Compaq Corp., and Advance/Newhouse. In June of 2000, AT&T acquired MediaOne and assumed their ownership interest in Road Runner."
That list yields a couple of possibilities, seem pretty important in the broadband market. I'd almost make the connection with Excite via AT&T's share in the @home broadband project. Good luck in your searching.
Road Runner is just as notorious as @home for harboring spider runners. I'd bet it was just some joe user with a new spider trying it out on your site while he slept. We get them all the time (daily) on some sites.