ReadPixels from rendertexture with multi-camera setup fails on iOS

Hey guys,

I'm making a screenshot of a game level which uses a multi-camera setup, while the game view is obscured by another (one more) camera (so that the user doesn't even know what is happening behind the visible game menu).

The following code works perfectly in Editor, however on iOS I get a gray texture and a weird error message:
Reading pixels out of bounds of the current active render texture

Any ideas?

Code (CSharp):

1.     /*
2.            
3.             rt = new RenderTexture(Screen.width, Screen.height , 24 , RenderTextureFormat.ARGB32);
4.             rt.useMipMap = false;
5.             rt.antiAliasing =1;
6.             RenderTexture.active = rt;
7.             CameraHolder.one.OverlayCam.targetTexture = rt;
8.            
9.             */
10.            
11.             screenShot = new Texture2D((int)rect.height, (int)rect.height, TextureFormat.RGB24, false);
12.            
13.             yield return frameEnd;
14.            
15.             RenderTexture.active = rt;
16.             CameraHolder.one.OverlayCam.targetTexture = rt;
17.            
18.             CameraHolder.one.BackgroundCam.Render();
19.             CameraHolder.one.MainCam.Render();
20.             CameraHolder.one.ScrollCam.Render();
21.             CameraHolder.one.OverlayCam.Render();
22.            
23.             int diff = ((int)rect.height - (int)rect.width) / 2;
24.            
25.             screenShot.ReadPixels(rect, diff, 0);
26.