Unbelievable error!

[Caius Aérobus]

I have 2 differents functions/slots (in the same class) in which I emit the same signal and...one of them works, that is the slot associated to this signal is executed, and the second one does not! I have made a copy-paste of the slot code so as to be sure that it was exactly the same and still this inbelievable error! To sum up my code:

class A
{
public slots:
  void sl(<some data type>);
};
class B
{
signals:
  void si(<some data type>);
public slots:
  void sl1() {emit si(<some data type>);};
  void sl2() {emit si(<some data type>);};
};
main()
{
  A a;
  B b;
  QObject::connect(B, SIGNAL(si(<some data type>)), A, SLOT(sl(<some data type>)));
  ...
}

class A
{
public slots:
  void sl(<some data type>);
};
class B
{
signals:
  void si(<some data type>);
public slots:
  void sl1() {emit si(<some data type>);};
  void sl2() {emit si(<some data type>);};
};
main()
{
  A a;
  B b;
  QObject::connect(B, SIGNAL(si(<some data type>)), A, SLOT(sl(<some data type>)));
  ...
}

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Of course <some data type> is identical everywhere.
Did anybody face a so strange story?