Posting a screenshot of the NGE would both be more concise and probably informative of what pins are unconnected. Most likely (especially if templated), there was a random, blank node created, which is linked to the final output. It is likely a mix material not linked to by anything, and linking from the correct, and still present mix node to the final output should fix your issue. I had this problem on a similarly complex material, so I'm just guessing based on that, as the wall of parameter sliders is far less easy to identify issues in.
The other variation, if the template or diffuse image was linked to multiple nodes, is that some of those links were re-linked to a newly created RGB node, screenshot follows.
All that was needed, was re-linking the Diffuse output to the Diffuse input of the two nodes, and the material was restored to normal. I've had both occur separate times of loading the same preset material, so I couldn't tell you which is more probable, but the fix is similar regardless, re-link nodes to their appropriate inputs, and all should be well. It can be tedious, but once fixed, can be copied/pasted to similar materials, you'd just have to change the diffuse and/or bump map to the correct one(s), much like a template.
You may need to smart unfold the solitary mix node you see, if the original material was pretty complex, do this by right-clicking the node and selecting it from the context menu.
Edit: Re-looking at the material in 1.2, it may have something to do with the way it collapses the material. I've never saved this material in 2.15, but the template has been collapsed (not by me), and cannot be unfolded in 1.2, though it still renders correctly. Perhaps something about this collapse process injects substitute nodes when 2.15 attempts to read it, as there are new node types available, and the templates may be incompatible somehow. This is purely speculation on my part, and since the material itself still seems unaffected, I can't quite call it a bug (glitch/unintended effect of adding new node types?). Regardless, the fix above works within 2.15 to restore the material, so I guess this is more of an informational side-note.
