Ok, first off, this is not explicitly about Boost, which I know is against the Boost guidelines, but I hope you'll all forgive me. Indirectly it is through trying to use Boost that i've bumped into this. A little code snippet... #include <cstddef> template < typename T, std :: size_t sz > struct Block { typedef T type[ sz ][ sz ]; }; template < typename T > void assign( T & assignee, const T & value ); template < typename T, std :: size_t sz > void assign( T ( & assignee )[ sz ], const T ( & value )[ sz ] ); int main( ) { Block< int, 16 > :: type a; const Block< int, 16 > :: type b = { }; assign( a, b ); } This compiles under Gcc & Comeau, but MS VisStudio reckons the call to assign in main is ambiguous. Any thoughts? Also, if I put all the template declarations in an anonymous namespace, Comeau fails to compile, while Gcc is still ok! Have we encountered this before, and is there a known work around? Thanks. - Rob.