Exception "deleted entity passed to persist"

[hager]

hello,
I have a OneToMany relation between Pret and EcheancePret.
when i create one Pret, a list of EcheancePret is automaticaly created and inserted in the database,
but when i want to update my Pret, i have to delete the list of EcheancePret, create and insert a new one,
this is my code:

/*** PretHome.java ***/

Set<EcheancePret>listeEcheancePret=this.getInstance().getEcheancePrets();
for(EcheancePret echeance : listeEcheancePret)
{
this.echeancePretHome.setInstance(echeance);
this.echeancePretHome.remove();
}

but i have an exception :

deleted entity passed to persist: [com.fitnetapplication.resources.model.EcheancePret#<null>]

what can i do?
please help me!
thx.

[manuelpalacio]

You have to remove the EcheancePret from the EcheancePrets collection in Pret before you can delete it.