There are lots of participants in that topic from tomshardware but sooner or later they all seemed to find a solution...
A BIOS change
Changing SATA port connections (if a SATA drive)
Changing USB port connections (if a USB drive)
Turning off system protection on the external drive (a good idea)
System Protection should really only be enabled on your system drive anyway:

I know it seems like a Windows problem at the moment but if it was a bug in Windows none of those folks would have gotten their stuff to work... but they all resolved the issue (sooner or later) by making various adjustments. If it was a Windows bug it
seems they would still be having the problems.
I quit using Windows backup a long time ago because it can be troublesome and has very limited options and flexibility. Microsoft is not in the backup/restore business so you might consider looking at alternative products from companies that are in the
backup/restore business where that is all they do all day long.
Popular lately (and what I switched to is Marcium Reflect:
http://www.macrium.com/
You can get the free version or use the Home version free for 30 days.
I get the feeling that the problem lies somewhere with the sheer size of your backup with image (how big is it) and your backup with no image (how big is it). Somehow Windows is having trouble digesting the large one so even if you were to use another backup
program you still might have the same problem if your backup with image is large, but remember all those folks in tomshardware got their stuff working eventually.
It is not something I know how to reproduce to troubleshoot. I may make some adjustments here and there to see if I can reproduce it