Hi Monil,
I was just able to successfully retrieve an image from a 9014 so it doesn't seem to be a general problem with 9014s and System Configuration 5.6. I did realize that my RIO drivers are 13.0 so I can upgrade that and try again.
You mentioned that you are able to take the image of a 9073. Have you tried replicating the software installed on the 9073 on the 9014? I don't know how doable this is with your set-up, but that would allow us to isolate whether the problem has to do with the installed software.
Also, can you try taking an image using the System Configuration VIs. There is an example in the Example Finder called Get and Set Real-Time Real-Time System Image.vi. You should be able to just run that. This will take RAD out of the picture, though I suspect you will get the same error.
Have you tried looking at the console out of the cRIO as you try to image it to see if it's reporting any errors?