Can you post the normal map and let us know where the dark logs occur in the texture space? It could be that the dark regions are caused by the normal map flipping the normals.
One thing you could check is to export the displaced normals right out of Maya, and compare it with the output of CrazyBump to see if there is anything grossly different between the two. Did you have shape recognition on when you exported the normals from CrazyBump?
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