It looks like someone may be using the Gecko engine to create a bot, for what purpose i do not know. I found some browser stats going back to Monday 05/Feb/2001 on a Google search for Gecko/20010129 so it's been around for at least a few months, but if this guy hit you that many times I would say they have a bit of fine tuning to do on their project. If writing them yields some answers, let us know!
descr: Planet Online Limited
descr: The White House
descr: Melbourne St.
descr: Leeds LS2 7PS United Kingdom
See [theplanet.net...] which is an e-business solutions company.
(From Netscape )
"...Gecko is Netscape's revolutionary next generation browser engine. It features industry-leading, fully compliant standards support (including HTML 4.0, XML, CSS, and DOM) and is small, fast, and modular."
a search on Gecko/20010129 also gave these results.
(Galeon is a Gnome based browser)...
"Galeon gives the following UA string: Mozilla/5.0 (X11; U; Linux 2.4.1 i686, en-US; Galeon) Gecko/20010129"