Weird Redirection Problem

I wanted one of my posts to have another category so I added it (original: documentaries, new: hip-hop). It changed the url from http://silencenogood.net/documentaries/hyphy-movement-story/ to http://silencenogood.net/hip-hop/hyphy-movement-story/ but I wanted to keep the original so I removed the hip-hop category. Now when you go to either link it starts redirecting to the other link back and forth…. anyone know how to fix this??

Thanks 🙂