I'm rather unsure about what is causing this, but I get an internal compiler error in Visual C++ 7.1 when using BGL in some specific circumstances. I have a graph defined in class Graph defined as such: typedef property<edge_feedback_t, bool> EdgeFeedback; typedef property<edge_sourcejack_t, IAudioOutputJack*, EdgeFeedback> EdgeSourceJack; typedef property<edge_destinationjack_t, IAudioInputJack*, EdgeSourceJack> EdgeDestinationJack; typedef EdgeDestinationJack EdgeProperty; typedef boost::property<boost::vertex_index_t, int> VertexIndexProp; typedef property<vertex_name_t, nsCOMPtr<IAudioModule>, VertexIndexProp> VertexProperty; typedef adjacency_list<listS, listS, bidirectionalS, VertexProperty, EdgeProperty> graphdata; typedef graph_traits < graphdata >::vertex_descriptor vertdsc; This definition works fine in the graph.cpp file that implements the class Graph. However, when I use graph.h in another cpp file, I get bizarre compiler errors: c:\Boost\include\boost -1_31\boost\mpl\aux_\preprocessed\plain\apply.hpp(50) : fatal error C1001: INTERNAL COMPILER ERROR After some trial and error, I narrowed the problem down to needing to have a != between two oedge_iterators _somewhere_ in the cpp file including graph.h. Simply putting the following function into my other files will cause them to compile just fine: void makeVChappy() { typedef graph_traits< Graph::graphdata >::out_edge_iterator oedge_iterator; oedge_iterator oiter, oend; oiter != oend; } I'm a a complete loss as to how this could be happening, but since I have a work-around for now, I'm not going to push the issue too much further at the moment --- I just thought I'd bring this to your attention, and see if anyone knows of a more elegant solution.