HC-SR501 PIR sensor problem

Hi I am having an issue with the HC-SR501 PIR sensor.
I have followed these instructions How to use Pyroelectric ("Passive") Infrared Sensors (PIR)
However, when I just try to connect a 9v battery and an LED to the sensor, it just blinks (indicating that it has detected movement).. even when there hasn't been any.
I have tried attaching it to the Arduino as per the example, and have the same problem.

Here is a video of my sensor

Here are a couple of pictures of my sensor:
https://drive.google.com/file/d/0By1bgqyE-fqqbUNvNmFpWV9fakE/edit?usp=sharing
https://drive.google.com/file/d/0By1bgqyE-fqqTzh2ODd0RHVEeUU/edit?usp=sharing

If you have any ideas on how to resolve this issue, please let me know.

Looks like I had a defective sensor.
Using a second sensor, I now believe that I have it working.
Here is link to the video of the (2nd) sensor in action.

And anyone who wants to know the parts and sketch I used to put it all together, have a look at my blog for full details
http://arduinobasics.blogspot.com/2013/12/pir-sensor-part-1.html

Although I had no answers from anyone in this forum, I managed to get some very valuable help from a number of people from the Arduino Community over at Google+... I hope this tutorial and video will help anyone who encounters the same issues that I did.
Good luck