When you zoom in to the LIDAR point data in TerraScan, the points disappear. They reappear when you zoom back out.
Probable Resolution #1:
Are there any vector elements well above or below the surface of the points? Bring the vector to the elevation of the point data.
Probable Resolution #2:
Confirm that your Move Camera is off (click the Zoom In button on the affected View), and that Camera is not active in View Attributes.