See normally to read/create a SharedObject you write code like this:
var so:SharedObject = SharedObject.getLocal( "mySO" );
The above line of code will read the SharedObject called mySO or create one if it does not already exist in a similar folder structure as the one that follows (varies based on OS - I am using Vista):
Since the SharedObject is created in a folder specific to SWF A (see the "\localhost\SWFA" above), SWF B, will not be able to read this SharedObject, thus the both applications cannot share data between eachother.
In order to solve this, you must specify an additional parameter to the getLocal() method call to tell it to save the SharedObject in a folder location accessible by both applications. An example is:
var so:SharedObject = SharedObject.getLocal( "mySO", "/" );
What this will do now is create the SharedObject in the following folder structure:
Hope this is helpful to some when working with SharedObjects. It is a simple, yet primitive way to share data amongst two Flex applications without requiring the use of a server of any kind.