From Forum Nokia Wiki

ID	KIJ000521	Creation date	December 19, 2006
Platform	S60 1st Edition S60 2nd Edition S60 3rd Edition Series 80 2nd Edition	Devices
Category		Subcategory

Keywords (APIs, classes, methods, functions):

Description

Because of the Symbian MIDlet installation process and how the MIDlets are registered as installed applications on Symbian OS phones, MIDlets installed on a memory card using one phone cannot be executed on other phones. Also if the phone memory is formatted, the MIDlets installed on the memory card cannot be executed unless they are re-installed. In these kinds of situations the MIDlet icon might be visible in the Application menu, but when the user tries to launch such a MIDlet, nothing happens.
This affects all MIDlets, both signed and unsigned MIDlets.