A change that was implemented at Win 7 was to run users in an entirely different session to the operating system as a security measure. System processes cannot interact with the desktop as was the case with XP; neither can you start a "system" command prompt using the AT scheduler. It is possible to enable interaction with the desktop but this forces a UAC message to pop up each time a desktop event tries to take place, and even then it does not work a lot of the time. No doubt the same security model is being used for Windows 8.
There are other techniques to communicate between different sessions - such as named pipes, but I don't believe there is anything like that implemented in Ghost at this time.
The safest way to proceed, IMHO, is to run sysprep so that it shuts the machine down at the end, then boot to WinPE and image from there. It may take a bit more effort but should give you more reliable results.
There is a very long thread about "When will Ghost 3 come?" which is worth reading, especially the last 30-50 posts, as it will give you a flavour of what is happening in Ghost development.