Hi, I'm having problems with the unit test framework when I try to run it in release mode. My compiler is VC++ 6 sp6. The unit test executable I'm building is "Using MFC as a shared DLL" and is set to use the "Multithreaded DLL" runtime library. The test subject code that is linked to this app is built with the same settings. I'm linking with libboost_unit_test_framework-vc6-mt-1_33.lib. The problem is that when the unit test starts to execute it fails with an access violation. In debug build it works fine. I enabled some debug info in the release build and found that what seems to be happening is a deallocation of "invalid" heap memory, which I'm guessing could be a result of different runtime libs being used. The stack trace at the point of the crash is included below. Has anyone had the same kind of problem and perhaps found a solution? Best regards, Niklas Wiberg NTDLL! 7c901230() NTDLL! 7c96cd80() NTDLL! 7c960af8() KERNEL32! 7c85e7af() _CrtIsValidHeapPointer(const void * 0x003b2418) line 1697 _free_dbg_lk(void * 0x003b2418, int 1) line 1044 + 9 bytes _free_dbg(void * 0x003b2418, int 1) line 1001 + 13 bytes free(void * 0x003b2418) line 956 + 11 bytes operator delete(void * 0x003b2418) line 7 + 10 bytes std::allocator<char>::deallocate(void * 0x003b2418, unsigned int 33) line 64 + 16 bytes std::basic_string::_Tidy(unsigned char 1) line 592 std::basic_string::~basic_string() line 59 + 17 bytes boost::filesystem::path::m_path_append(const std::basic_string & {0x0032f9f1 "D:\dev\UnitTest"}, unsigned char (const std::basic_string &)* 0x0054f9b3 boost::filesystem::native(const std::basic_string &)) line 351 boost::filesystem::path::path(const char * 0x0032f988, unsigned char (const std::basic_string &)* 0x0054f9b3 boost::filesystem::native(const std::basic_string &)) line 220 + 37 bytes boost::filesystem::current_path() line 803 + 22 bytes boost::filesystem::initial_path() line 810 + 28 bytes init_unit_test_suite(int 1, char * * 0x003b2da0) line 19 + 5 bytes UNITTEST! boost::unit_test::framework::init(int,char * * const) + 201 bytes UNITTEST! main + 54 bytes UNITTEST! mainCRTStartup + 227 bytes KERNEL32! 7c816d4f()