Pen Tool Cursors
When working in any Adobe application, you need to pay attention to the cursor as you work with tools. The Pen tool cursor in Illustrator tells you a story (a really short story). So it's important to watch what Illustrator's Pen tool cursor is telling you in certain situations. Figure 3 shows each of the cursors that appear as you work with the Pen tool. Note that if the Caps Lock key is pressed, the cursor changes to a "Precise" cursor (which looks like an X at first).
Figure 3 Pen tool cursors in Illustrator.