Bumpmapping bug

I tried adding bump map to my tank object, it worked great. I set it to always follow, always have the same angle when my tank moves. One problem though is when I rotate this giant square of white keeps resizing around the tank, looks weird.

Anyone else get this? Am I doing something wrong?

From Bumpmapping:

[quote:367j6rha]...normal maps cannot be rotated, since the 3D data is only valid for an angle of 0 degrees. If you want to apply bumpmapping to a rotating object, you can only use heightmapping.

i.e. use a height map and the Heightmapping shader for rotating lighting.