Channel01 - 10:49 pm on Jun 16, 2010 (gmt 0)
Yeah, I've had this same issue. As you alluded to, the negatives function as broad negatives would in Google. I don't believe there is a good work around outside of bidding down your broad match keywords to fend off the irrelevant clicks. It's not exactly a good way for Microsoft to maximize ad revenue.
I actually had an even worse example. In my situation, I had an ad group of Black Shoes keywords and just the search "black" was triggering my ads. That query was racking up clicks pretty heavily too so bidding down/pausing the broad terms was the only solution I could come up with.