it looks to me as if the bump map on on the mirrored side is reversed. Perhaps, the faces on the mirrored side need to have normals reversed. I don't know. Check normals by going, display>polygon componants>normals. If thats not the problem, perhaps it is the hard edge between the two halves. Select all the joining vertices, and merge them then select the the center edges and soften them. Hope that helps.