Error Code: An unhandled exception of type 'System.Runtime.InteropServices.SEHException' occurred in IsoModuleTest.exe Additional information: External component has thrown an exception. result in mlock.c Code: void __cdecl _unlock ( int locknum ) { /* * leave the critical section. */ LeaveCriticalSection( _locktable[locknum].lock ); } following usage: Code: Class A in h: vector *testVector; ClassA::ClassA() { testVector = new std::vector(); ... } ClassA:oSomething() { ClassB *classB = new ClassB(testVector); } Class B in h: vector *testVectorB; ClassB::ClassB(vector *testVector) { testVectorB = testVector; ... } I don't understand this weird error ! It would be very nice if someone can help me !? greets leon22