If you have Entourage 2008 configured to check a POP account, it has been reported that after applying the 12.2.3 update, Entourage may forget the password stored in the keychain for the POP account. Reentering the POP account password works temporarily, but you will keep getting prompted for the password in the future. Microsoft support it trying to narrow down the cause of this, and it may be related to having an iPhone or iPod Touch access the same POP accounts.