Having trouble with planar collision detection

Right now I'm using this function:

Code:

	bool planeCollision2d(vector2 plane1, vector2 plane2)
	{
		vector2 vec;
		vec = plane1 - plane2;
		if(vec.dot_product(normalized(plane1)) > 1)
		{
			return false;
		}
		else return true;
	}

In this way:

Code:

	void check_paddle_collision()
	{	
		if (planeCollision2d(border.topLeft, player1->paddle->getMaximum()))
		{
			player1->paddle->getLocation().y = 70;
		}
		else if(planeCollision2d(border.bottomLeft, player1->paddle->getMinimum()))
		{
			player1->paddle->getLocation().y = -70;
		}
		if (planeCollision2d(border.topRight, player2->paddle->getMaximum()))
		{
			player2->paddle->getLocation().y = 70;
		}
		else if(planeCollision2d(border.bottomRight, player2->paddle->getMinimum()))
		{
			player2->paddle->getLocation().y = -70;
		}	
	}

And everything appears to be working.

Is there anything wrong with what I'm doing?

On a side note -

Code:

		if(vec.dot_product(normalized(plane1)) > 1)
		{
			return false;
		}
		else return true;

is the same as

Code:

return vec.dot_product(normalized(plane1)) <= 1;

Okay actually it doesn't appear to be working.

It seems to work fine when I do this:

Code:

	void check_paddle_collision()
	{	
		if (planeCollision2d(border.topLeft, player1->paddle->getMaximum()))
		{
			player1->paddle->getLocation().y = 70;
		}
		else if(planeCollision2d(border.bottomLeft, player1->paddle->getMinimum()))
		{
			player1->paddle->getLocation().y = -70;
		}
		if (planeCollision2d(border.topRight, player2->paddle->getMaximum()))
		{
			player2->paddle->getLocation().y = 70;
		}
		else if(planeCollision2d(border.bottomRight, player2->paddle->getMinimum()))
		{
			player2->paddle->getLocation().y = -70;
		}	
	}

But not when I do this:

Code:

		if(ball->getVelocity().y > 0)
		{
			if (planeCollision2d(border.topRight, ball->getMaximum()))
			{
				reverse_y_velocity(ball->getVelocity());
			}
		}