On a (possibly) related note, I'm trying to use the above subgraph in kruskal_minimum_spanning_tree(), but it's giving me an error about

error C2039: 'vertex_bundled' : is not a member of 'boost::subgraph<Graph>'

This was patched in trunk, but didn't for some reason, it hasn't been merged into the release branch. It'll appear in 1.40.
Andrew Sutton