That is the format used by XBT trackers. XBT is used by many of the higher-traffic private sites. It doesn't like µTorrent 2.0b's omission of the parameter 'event=started' to the initial contact with the announce URI. According to theory.org's version of the BitTorrent specification, it is right to: "started: The first request to the tracker must include the event key with this value". The version at bittorrent.org doesn't say the same so clearly, but the implication is certainly there. Needs fixing. Not as far as I can see.