This issue is specific to Vista and Windows Server 2008 platforms.
The iPrint dialog box is intercepted on Vista and Windows Server 2008
The iPrint dialog box on Vista and Windows Server 2008, sometimes displays the Interactive Services dialog box .
Vista restricts applications from being launched from the system context. This has been fixed in iPrint, but there might be random situations where it still happens.
To avoid seeing this dialog box, the interactive service needs to be stopped by using the following procedure:
Double-click service from the list.