I've tracked down the cause of my errors wrt kruskal_minimum_spanning_tree. Recently the Boost Concept Checking Library adopted a new naming scheme, deprecating those classes whose names that have the "Concept" suffix in favor of the corresponding classes without the suffix. AFAICS the BGL algorithms are still using the concept checking classes with the old names, which should be okay until a future release removes the old classes. The problem lies in <boost/concept/detail/concept_def.hpp>, line 26: the ctor that was supposed to satisfy GCC 3.4.4 is fouling up my own compiler, GCC 3.4.2 (MinGW). The ideal solution would be to update the BGL algorithms to use the new naming scheme. Cromwell D. Enage __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com