Error on Default Method of Signature object

Hi,

I want to use the Signature.Default() method of the GW Object API (v8.0.3) to change the signature which will be used when an email is sent.

An error occurs with the following message : " Member not found"
The Signature objet is returned from the Account.Signatures.Item( n ) and the properties are ok (name, type, etc..)

Thanks for any help,

Thierry