[HarvestOfSorrow]

I found my mistake lol XD
It's so simple, its almost silly.
What i did....was trying to use a material that had map(diffuse-Ambient/Reflective Occlusion) from mental ray, while i was importing it into a scene with default renderer.
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To solve the problem all you need to do is to assign a renderer which the material uses in the original scene or to uncheck the map in the rollout.
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P.S. thx for the link Minimus, i'll get the service pack now :).