Thanks also to you DataMiser,
We actually try to debugging the OCX in the register and unregister function, watching the output on exit too. About probable reference to an object or class upon termination of the program we can almost say that is all clean, nothing more then some wrong releasing of memory in a part of our OCX (is divided in 3 main parts, but also after an not so easy operation of separation of those , our "Class not Registered" error still comes).