Problem with Havok math classes.

If I try to use any of the Havok math classes (hkMatrix4, hkTransform) as members of a class my software crashes when trying to use them. Ex.

class TestClass
{
public:
    hkMatrix4    _t1;

    void test();

};
void TestClass::test()
{
    _t1.setIdentity();
}

void TestClass::test2()
{

   hkMatrix4    t2;
    t2.setIdentity();
}

The above code will crash on test1 but not test2. Any one know whats going on here?

Cheers,

Keith