This error can occur when you are trying to automate a Ghostcast session with the -sure switch. What is going on is that the the disk is not specified. In a non-automated Ghostcast session, the user specifies the source (for image cration) or destination (for image restore). When adding the -sure switch, the -clone switch either needs to be included in the boot media, or the disk number needs to be specified in the Ghostcast Server session in the "Client command line options" area. this particularly useful in a PXE deployment environment when the switches -ja=<sessionname> -sure are typically added.