Not a bug with the engine at all. But the set of nice shaders Conitec plans to offer that developers can modify to suit their needs isn't out yet (but it does have a "high" priority on the forecast list) So unless you're a hotshot shader programmer, you're at the mercy of whatever's offered up on the boards--and the Normal Mapping shader that's been generously offered so far just isn't very robust yet.
http://www.conitecserver.com/ubbthreads/showflat.php?Cat=&Number=403149&page=&view=&sb=5&o=&fpart=3&vc=1