Problem with GuiTexture behind the 3d objects

i also make 2 cameras

1. for background guiTexture and select background layer which i made for background set its culling mask to background layer, clear flag to Depth only. and Depth to -1.

2. 2nd camera for other layers and its clear flag to Depth only. and its Depth 1. also try Depth to 0.

now problem is this 3d objects showing front of guiTexture in just game preview when i playing the game all the 3dObjects are invisible.. ?

Thanks for your time...