使用队列的幻像错误（STL库），Windows / MingW / G ++

//The queue is defined Globally but the problem happens even
//if i define it locally and pass it by reference.
queue<pair<int,int> > Q;

void yadayada ()
{
    //initialize Q
    while (!Q.empty())
        Q.pop();   //CORE DUMP, what the hell?
}

int yadayada2(...) 
{
//code...code...code

//the element in front is (4,20)
front = Q.front(); Q.pop();

cout << \"(\" << front.first << \",\" << front.second << \")\" << endl;
//prints: (0,0) 
//what the hell?

//correctly returns 20
return front.second;
}

int main()
{
//code...code...code 

//prints 20!
cout << yadayada2 << endl;
}