Fernando,
I don't think this has to do with your error, but

F> Property StoredProcHasDML is 'True'.

AFAIK this should be false unless you modify data inside the SP. "DML"
here has a slightly unusual meaning. And

F> ExtCaixa.ParamByName('INCaixa').AsDateTime:=StrToInt(EdtCx.Text);

is this a typo? I don't think you really want to specify dates in
numeric form.

Also, have you tried to prepare the statement each time you execute
it, and unprepare it afterwards, to see if it makes any difference?

Ciao
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