PS: Pen Tool... Drawing Curves then straight lines

Well I am getting better with the PS pen tool but I just ran into an annoying problem. Well I drew a curve and now I want to make a straight line.

when I first start drawing a new path with the pen, if I click once and then click again at a different piont (without holding down), it creates a straight line. The problem I am running into is when I click and then click and hold (then minapulate the curve), afterward, whenever I click it creates a curve, not a straight line.

Basically, does anyone know how to draw a curve with a line, using the pen tool, then draw a stright line, continueing the curved path with the pen tool? Thanks

MIke