Hello, Sorry to ask this question but I investigate and I didn't find any previous message. I try to use boost::filename::is_directory( path) in my code developed on visual studio 2008. In debug mode, I have an error on this function and specificaly at file_status result( detail::status_api( ph.external_file_string(), ec ) ); in operations.hpp. (Detail status crashes, it seems). In release mode, no problem everything is fine, my path is valid and my program is running.... And yes, my path is valid. I have boost 1.40, the compilation option for boost and my program are the same. The linkage is valid (I checked that my compiled libraries are used). So anyone has a clue for this bug? Because I'd like to understand and stay in debug mode to track bugs. Thanks by advance