In experimenting with bump mapping, I created a material with diffuse, specular and normal (bump) channels.  When I did not get expected results, I discovered that the exporter does not take the .bmp format which I used for the normal and specular images.  After deleting these channel as well as the UVTex associated with the mesh (a simple plane), I found that the object retained a speckled pattern that persists even after assigning a new material to the object.

I am using Blender 2.49a, Yafaray 0,1,1 and Windows Vista 32.

Edit:  After reloading this file, the problem has gone away for me.  So this report can be closed.