Based on the fact you (and therefore probably she) called it the "naked mile" rather than the "pumpkin run," I'd guess you're referring to the "Nearly Naked Mile," a clothing fundraiser that just took place a couple of days ago at UC-Boulder.
Website is here:
http://www.cuherd.com/2008/05/03/nea...lothing-drive/
Photo attached.
This would be cool to look at, since as your pic indicates some attractive girls participate in this, but it doesn't sound like there's any actual nudity.