Since the solution to this problem seems to be deleting the userprefs file I would love to find someone that could compare a fresh file with a corrupt one and tell me what the hell the thing is that gets switched on to display these annoying shader nodes and why the bloody hell there does not appear to be any way to turn the behavior off without destroying the userprefs file!

As I said I have filed several bug reports to autodesk with userprefs.mel files and they just go into a black hole and short of the auto generated receipt email I never hear a word back from autodesk. I have posted the description in the area forums and once again I never see a response that acknowledges the problem and all I get is all kinds of random and sometimes just insane suggestions.