When you are adding the image into the page you can see the image on the server and select it correct? When you select the image you can see the image in your editor before you submit the results correct? If so when you see the image in the editor what is the source of the image? This should all just be a matter of getting the paths to work correctly with the structure of your site, if we can see where the image is comming from when it is working correctly and compare that to the value that the end user is seeing it should clear up our understanding of where the image is coming from and what should be done to the paths to correct it.
Please post back with this info and if you can't get to it let me know and I will open a ticket with you so we can look at this on your live server.