You must encode it properly: http://graph.facebook.com/http%3A%2F%2Fwww.twitter....

TomasSedovic on March 20, 2011 | parent | context | favorite | on: See how many times a URL has been shared on Facebo...

You must encode it properly:

http://graph.facebook.com/http%3A%2F%2Fwww.twitter.com%2F%23...

Note that encoding '#' as %23 is sufficient.

However, it doesn't show any shares and I'm not sure if that means nobody shared your twitter URL on facebook or if there's another problem somewhere.