Adobe AIR has a feature called EncryptedLocalStore, which is where apps can store potentially sensitive data that needs to be secure or safeguarded from other applications. Examples of things you might want to store there are user passwords, SSL connection data, or even something slightly more mundane such as e-mail addresses.
var els = air.EncryptedLocalStore; // for convenience var password = els.getItem('MyPassword'); // returns string (or null) var blank = els.getItem(); // error
However, sometimes you may find that calls to
EncryptedLocalStore.setItem are failing, and catching
the error doesn't produce any useful information. In this case,
the application's EncryptedLocalStore may have become corrupted.
After installation, if you change the contents of any installed
files, that application's signature will have changed, and it will
no longer be able to access its EncryptedLocalStore.
This is actually a pretty handy security feature, especially since HTML AIR apps have their source code available in plain text after installation. This safeguards against users or other programs changing your code to get sensitive data from your EncryptedLocalStore.
I just wanted to mention this problem because it is not (yet) a thoroughly documented error situation. Reinstalling the application will fix the problem.