The first screenshot doesn't have any of the GP messages (see Geoprocessing>Results) - I would look at those messages and see if you get any clues from them.
I suggest turning off background processing (Geoprocessing > Options > uncheck Enable) and see if that makes any difference.
One more thing spaces and any special characters (besides _) in your pathname may work for most tools most of the time but is not advisable, especially with Spatial Analyst tools.
I did uncheck enabling
And the message :
ERROR 010328: Syntax error at or near symbol SPACE.
ERROR 010267: Syntax error in parsing grid expression.
Failed to execute (CreateSignatures).
You didn't show any of your pathnames used. My guess is you have spaces in your path or raster names.