System Chimes but Does Not Arm

From X10Wiki

Question

Why does my security system quickly chime and not arm when I try to arm it?

Answer

If your security alarm is chiming quickly when you try to Arm it, individual sensors may have been installed multiple times. Each sensor can only occupy one zone at a time, so the remaining zones that are installed are "ghost" zones, and they prevent the base console from arming. The console should have the same number of zones as you have Door/Window and Motion sensors.

In order to clear up the problem, unplug the base console from the wall and remove the battery backup. This will clear out the memory in the console and allow you to re-install all sensors and remotes. As you re-install the sensors, be careful not to trip them more than once. Just hit the Test button on each one, while the console is in the "Install" position. Tripping a sensor includes opening a door or window that it is protecting, as well as walking in front of a live motion detector. You can turn the motion detector to the wall to complete the installation without any errors.