Symptom

When you open a help file (e.g. help.chm or the P2 Guidance Module p2gm.chm) the navigation tree shows in the left hand pane, but in the right hand pane you get a message such as:

Navigation Cancelled

Solution

1. Open Windows Explorer and navigate to the file.
2. Right-click the .chm file, select Properties.
3. Click the Unblock button.