>it was already checked to .T.
>
>>>Sorry, I done it , but if someone thinks is not the right way, please,let me know...
>>>I release the formset in the unload method of the main form
>>> release thisformset
>>>and it seems to work

Mi sembra di ricordare che questo è un bug di Autorelease.
Questo è semplice se il set ha un form radice, ma con un gruppo di forms è dura.

I think it is a bug.
This is simple if you have a Main Form, but if you want implement a Forms Pool
this task is more complex
( any Form have to check ThisFormSet.FormCount=0 in Unload event )

IF EMPTY(m.ThisFormSet.FormCount) AND m.ThisFormSet.Autorelease
  ThisFormSet.Release
ENDIF

Sfortunatamente non si può definire una sottoclasse di un formset in un VCX.

Unfortunately the subclassing a FormSet baseclass into the VCX is not possible,
and then all is more complex.