Holy weird hostnames, Batman, I just realized that a bizarre issue I've been seeing is the same as yours.
My computer as well has a hostname that I can't seem to change (or, for that matter, figure out where it's coming from). Except in my case, the hostname is the same as a work laptop that, so far as I can remember, I've never had even plugged into my home computer, let alone ever set the hostname to the same value.
This has got to be some sort of Tiger bug, as I've NEVER seen it happen on a dozen different 10.3 installs, where the hostname was always a spaces-and-punctuation-removed version of what's in the Sharing section of System Preferences.
Figured out anything yet? /etc/hosts doesn't say a thing about it, and /etc/hostconfig doesn't even have the "AUTOMATIC" paramater, let alone anything hardwired, as in the link above.
Where the heck is this value coming from?