Whats the action of the block? In the manual is the example

Code:
#include "mtlFX.c"
...
action bumpy_warrior()
{
  my.skill41 = floatv(50);  // facAmbient
  my.skill42 = floatv(50);  // facDiff
  my.skill43 = floatv(50);  // facSpec
  my.skill44 = floatv(50);  // shininess
  my.material = mtl_specBump();
  ...
}


http://manual.conitec.net/amaterial2.htm

Have you tried other values than 50?