With the new release of the BlackBerry Tablet SDK 1.0.1 and the release of the PlayBook device, there is a new application capability that is required to access the PIN and serial number of the device. To access these properties in the SDK you can use the Device.pin and Device.serialNumber properties. However, if accessing these you must make sure you take into consideration that these values may be null. This will happen if the user does not grant your application permission to read those values. And we all know what happens when you try to access a null object in ActionScript. Crashy Crashy. Here is the documentation for the Device class as well as more information on add permissions to your application.
You will also need to re-compile your application with the 1.0.1 SDK in order to make this work correctly.