File or Folder does not exist

I'm having a wierd problem with a png image which generates an error in my script.

I'm building a UI using the group constructor, here is the line code I'm using to load the image:

myImg:Image{text:'',image:'(image_folder)/image.png', alignment:['left','top']}

The script runs with one image but not another one which is also a png of the same dimensions, bit depth etc. For some reason I get the 'file or folder does not exist' error message. If I replace the image with a known good one the script works.

I've re-generated the image a dozen times. Still no joy.

I'm not a total noob, though I infrequently write scripts and am completely prepared to learn I've made totally maverick error.

Any thoughts?