If statement doesn't want to do else

[sjaguar13]

                if(x1==x2)
	{
		if(x1==x3||x1==x4)
		{
			setDef();
			return false;
		}
	}
	else if(x1==x3 && x1==x4)
	{
		setDef();
		return false;
	}
	else if(x2==x3 && x2==x4)
	{
		setDef();
		return false;
	}
	else if(y1==y2)
	{
		if(y1==y3||y1==y4)
		{
			setDef();
			return false;
		}
	}
	else if(y1==y3 && y1==y4)
	{
		setDef();
		return false;
	}
	else if(y2==y3 && y2==y4)
	{
		setDef();
		return false;
	}
	else
	{
		m_x[0] = x1;
		m_y[0] = y1;
		m_x[1] = x2;
		m_y[1] = y2;
		m_x[2] = x3;
		m_y[2] = y3;
		m_x[3] = x4;
		m_y[3] = y4;
		return true;
	}
	/*...It only works if I put this right here...*/
	m_x[0] = x1;
	m_y[0] = y1;
	m_x[1] = x2;
	m_y[1] = y2;
	m_x[2] = x3;
	m_y[2] = y3;
	m_x[3] = x4;
	m_y[3] = y4;
	return true;

When I set the m_x and m_y equal to x1 and y1 in the else, it just skips over it. I have to put it at the end or the coordinate pairs come out -8700302093. Why doesn't the else get called?