First, you may want to recalibrate the eInk side (Tech Support wil likely ask you to do that anyway). Also, try another EPUB that you know previously worked to see if it's not a file-specific problem (the file may be crashing/hanging the eInk software). Also see if the Journal works and allows you to write notes.

If the eInk still doesn't respond after that, then it sounds like a hardware failure, at which point you should contact www.entourageedge.com/support to arrange an RMA.