跟踪Vuforia后NGUI不可见

I am using Vuforia 4-2-3, the latest NGUI verion and Unity5.0.1.p3 My GUI works fine until I track a target. After that, my GUI is invisible However, the collision still works. So buttons are working, only I can't see sprites, textures or labels.I am using Vuforia 4-2-3, the latest NGUI verio