All the urls being indexed seem to be lp.php and dl.php. Both those pages send http redirect headers so I don't know if you can edit them to include a meta noindex and meta refresh instead of the http redirect or if that would screw things up. The meta noindex would keep google from indexing the url, right? If not then everything else I wrote is moot.
According to that the thing to do is allow google to crawl the url but then serve it with the noindex, nofollow meta tag.
That is, if p202 will not fuck up if you change from a http redirect to a meta redirect. I've just installed prosper so I'm not really sure how it works yet.
I just noticed indianman's post. That might work too.