Afer Effects CS5 Ver 10.0.0.458
Dell Latitude E6400
I am trying to create a mask on a clip using the pen tool, a task I've done hundreds of times. It has been a simple process hundreds of times, until this last time. Now, I click to place the first vertex, then click for the second. I am unable to add a third vertex. My pen tool pointer changes from the standard pen to a pen with a plus sign after I click the second vertex.
This is a behavior that seems to have started out of the blue. If there is some not-so-well-known setting that affects masks drawn with the pen tool, I don't know what it is or how I might have changed it.
Additionally, I cannot enter vertex edit mode (or whatever it is called). I use this often, as I rely on the ability to drag a marquee selection box around a group of vertices.
Possible clue: by switching to the pointer tool, then back to the pen tool, I can add vertices along the initial line segment. After adding a vertex and switching to the pointer, I can reposition the vertices, which gives me a V shape. Back to the pen tool and I am able to click the first vertex and close the mask. None of these things (adding/repositioning vertices, closing the mask path) were available as I was initially creating the mask.
Looking back on things, I suppose I could constantly switch between pen and pointer and get my masks created, but I want to understand what is happening and be sure it is not a symptom of a bigger problem.