From December 11 2009, users using Office 2003 will not be able to open or save Office 2003 documents protected with the Active Directory Rights Management Service (AD RMS) or Rights Management Services (RMS). The error below comes up while trying to open a protected document.
"Unexpected error occurred. Please try again later or contact your system administrator"
The expiry date for the license information within the definition file that is used by Office 2003 to enable IRM functionality is set to December 10, 2009. This problem occurs because the expiry date was not renewed.
A supported hotfix is available from Microsoft. More info here
A simple workaround is to open the protected document using Office 2007.