Classes as arguments

When passing a class as a parameter to another class' method, is there any thing I should bear in mind?   Maybe some overloading of the = operator, or something else?

I am getting a "Debug Assertion Failed" when the method is called.   I commented out the entire inside of the method, so the code now looks something like this:

======CODE=========
class A{
public:
    contructor();
    destructor();
    someMethods();
private:
    int someData;
    char someMoreData;
};

class B{
public:
    constructor();
    destructor();
    void brokenMethod(A instanceOfA);
private:
    int yetMoreData;
}

void B::brokenMethod(A instanceOfA)
{
    // ALL COMMENTED OUT
    cout << "Returning..." << endl;
}

int main(int argc, char** argv)
{
    A A;
    B B;
    cout << "Calling brokenMethod." << endl;
    B.brokenMethod(A);
    cout << "Returned."

    return 0;
}

======OUTPUT=========
The output looks like this:
Calling brokenMethod.
Returning...

======ERROR=========
Everything complies fine.   During runtime I get:
Debug Assertion Failed!
Program: <Path to my program>
File: dbgheap.c
Line: 1011
Expression: _CrtIsValidHeapPointer(pUserData)

As always, any help is super duper appreciated.

pdm