I wish I could help, but I am afraid I don't speak the language of the
app. Furthermore, as I do not have the sources of the app I
cannot really figure out what is failing. The difference between
this app and other ones is that they at least gave an exception
about which class is missing. Here I have no idea at all.

Regarding the WhatsApp application, I reported about this before
in this forum:
* I know there is a version that runs on a plain java virtual machine.
It runs on AWT/Swing which is not supported on JavaME.
* There is also a Java ME midlet version, but it requires a bunch of
Nokia S40 specific classes for which I have no implementation:

com.nokia.mid.s40.bg.BGUtils;
com.nokia.mid.s40.codec.DataDecoder;
com.nokia.mid.s40.codec.DataEncoder;
com.nokia.mid.s40.io.LocalMessageProtocolConnectio n;
com.nokia.mid.s40.io.LocalMessageProtocolServerCon nection;
com.nokia.mid.ui.CanvasGraphicsItem;
com.nokia.mid.ui.DeviceControl;
com.nokia.mid.ui.DirectGraphics;
com.nokia.mid.ui.DirectUtils;
com.nokia.mid.ui.lcdui.Indicator;
com.nokia.mid.ui.lcdui.IndicatorManager;
com.nokia.mid.ui.s40.TextEditor;
com.nokia.mid.ui.TextEditor;
com.nokia.mid.ui.TextEditorListener;

Davy