I was just working on a site that uses two url aliases for a couple of nodes. This happens because if the node is viewed in one context it would require a different styling. These different contexts are being controlled with the url alias. /about for the normal site and /iframe/about (for example. we are not using iframes).
Currently the path (as used in the body classes) are being generated with a call to drupal_get_path_alias. This doesn't get the actual path that is currently being viewed.
Use request_uri to get the actual path that is being requested.
Patch to follow.