The Mrr link that went wrong had this URL:
http://washingtonpost.com/wp-dyn/metro/A25302-2000Jun8.html%20/
And the link that went right had this URL:
http://washingtonpost.com/wp-dyn/metro/A25302-2000Jun8.html
So it must be that %20/ at the end that screwed things up. I don't understand these things.