I found the problem.  There is a folder in the ImageEditor folder, Temp, that has to be read/write.

 

For whatever reason, the image editor just failed to show the image, rather than giving an error.  I created a test to show you the problem and it did give the access error.  I don't know why, but it certainly cleared up the question as to the source of the problem.

 

Are there any other folders that need r/w permission?