If you imported the template, you may not be able to save the file as a *.CDR file, as you may be modifying the actual template file (*.CDT). Unless I am misunderstanding something. My guess is that the changes you are making to the template file is actually changing the template, instead of changing the applied images to that template (if that makes sense)?
If I am misunderstanding your dilema, please let me know. Just to verify, was this a Corel Draw template? And did you apply the image to the template, or did the image come already included in the template?