Cut Works Intermittently

Fireworks CS6

I use the following process pretty often:

In the VECTOR section, I select the "pen tool" to select an area I want to remove from an image.

Once it's selected, I then right click the area and select CONVER PATH TO MARQUE

At that point, I can right click and select CUT or select EDIT and CUT and the area I selected is removed.

The odd thing is, sometimes it works and then it just stops.  I can't determine what the action causes it to stop.

Any help would be great!