Hi
I am fairly new to NHbernate and am getting the following error:

a different object with the same identifier value was already associated with the session:

I have an Entity object which has a list of Invoices
I have an Invoice object which can have a sender (Entity) and a recepient (Entity)

Users can manually create invoices sent to them in a paper form so the process is:
1) User selects a sender from the repository (I get the entity using NHibernate)
2) Enters all the invoice details and saves
2)a) On the save process i create the invoice object and assign it the entity (sender) and a receipent (Entity) which is the logged in user
b) I then call saveorupdate method which then throws the mentioned error

I have also tried to set the invoice in the Entity object before calling saveorupdate method but same error

Can anybody point me in the right direction

Thanks