Didn´t I write that?^^
It is a problem with the engine as only the first four mipmaps are used. The latest beta allows up to ten mip maps, I tried it and it works fine now (with your example!).

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com