12 years on and on 10.8.2 and I had the same issue. It was as Alice mentioned above, down to Python, is specific numpy. To sort it out these days I had to Add/Remove programs to "change" ArcGIS desktop to remove Python. Then manually delete the Python folder, then do the change thing again to add it back on.
Amazing that the same error remains for over 12 years - plus it doesn't appear to be in the Esri KB as I have a call in and if it were in their KB I would have thought this easy fix would have been found straight away!