Not the same computer.... but I've ridden with my Cateye Mity 8 in all sorts of downpours for hours on end without any issue.
I always though dielectic (sp is wrong, I'm sure) grease on the contacts would be a great idea.... but I never have done it (and my pockets stay clean when I put my computer in them).

I wouldn't submerse it in water, but I wouldn't worry about it either.