Link between accounts

Hi

I added a new field ( type = look up) in the account page to manage relationship between accounts but it doesn't work; if I create a link a field for accounts linked to other ilist ( for example contacts) it works...why?
If a select a value for the custom field, when I save, the value added disappers

I noticed the same behaviour for the default fieled " parent account": I select a parent account choosing from the accounts list and then, when I save, the account choosed disappers.

Thank you for your attention

Silvia
Silvia Giacoletto