I update the unity from 4.0.0 to 4.1.5 and ngui from 2.6.2 to 2.6.3,
For too many reasons, we must use 2.6.3 with unity 4.1.5. However, I find the .setActive has some problems with UIImangeButton -- I set the active of a button to false, but the image still remains.

The left is the button whose active is true, and the right on whose active is false, however, the image still there.