Hey, I just saw that Altova has a new UML tool available. I just downloaded it myself so I don't know whether it is any good, but based on other Altova I think it could be a great tool. The URL is:
http://www.altova.com/download_umodel.html They have a half price sale going on now so you can get a license for only $129 (not bad).
(I also recently downloaded Enterprise Architect 5.0 which has some great improvements. If Altova's tool doesn't turn out to be any good I would highly recommend EA 5.0)