>I have the following code in MAIN.prg:
>
>SET CLASSLIB TO test
>PUBLIC oApp
>oApp = CREATEOBJECT("APP")
>
>This runs the INIT which in turn fires my METHOD this.startup() which creates the menu and the READ EVENTS.
>
>I launch a form from the menu with 1 button CLICK oApp.cMsg = "test" This generates an error the oApp is not an object.

this is the key to your problem.
before you issue the SET CLASSLIB TO find out what the SET('DEFAULT') OR
SET('PATH') are equal to.

your SET CLASSLIB TO command is not working and VFP does not know where the
visual class library called 'test' is.

also,
try issuing
=TYPE('oApp')
to see if an object was created.