I'm using the latest .NET version of CE on a form page which also contains a calendar control. The form page is used to update data in a database so I populate the fields with content from the database. The CE control populates unless the calendar control is used.  After selecting a date, the content in the CE control vanishes - leaving a blank CE window.  The other non-CE fields do not vanish....

Seems that a postback will clear the CE window. 

Does anyone know  a way around this?

I've created a application with calendar control, using postback without any problems.

Have you checked your Page_Load method for any Editor1.text  initialization code?
If found, wrap it into a  if (!IsPostBack) block.