RenderTexture not working when in WebPlayer, unless in fullscreen

The following will work when in stand alone, and when on webplayer fullscreen mode, but will give odd results when in webplayer windowed mode.

 using UnityEngine;
 using System.Collections;
 public class CaptureScreenThumbnail : MonoBehaviour
 {       
         private Texture2D _capture;
         private Vector2 _size;
         
         // Use this for initialization
         void Start () {
             _size = new Vector2(300, 200);
             _capture = new Texture2D((int)_size.x, (int)_size.y, TextureFormat.RGB24, false);
         }
     
         void OnGUI () {
             if (GUI.Button(new Rect(0,300,40,40), "||"))
             {
                 StartCoroutine (CaptureThumbnail (_size));
             }
             GUI.DrawTexture(new Rect(0,0,_capture.width, _capture.height), _capture);
         }
     
         private IEnumerator CaptureThumbnail (Vector2 size)
         {
             // creating a Texture to Render to, the size of the thumbnail
             RenderTexture myRenderTexture = new RenderTexture((int)size.x, (int)size.y, 24);
             myRenderTexture.Create();
             
             // Setting the Camera to Render to the Texture
             Camera.main.targetTexture = myRenderTexture;
             
             // Setting the Texture to be the Active Texture to read from
             RenderTexture.active = myRenderTexture;
             
             // Creating a new Texture2D
             Texture2D myTexture2D = new Texture2D ((int)size.x, (int)size.y, TextureFormat.RGB24, false);
             
             // Turning GUI Layer off
             Camera.main.GetComponent<GUILayer>().enabled = false;
             
             // Wait for the Frame to be fully rendered
             yield return new WaitForEndOfFrame();
             
             // Read pixels from the Render Texture into the Texture 2D
             myTexture2D.ReadPixels(new Rect(0, 0, myRenderTexture.width, myRenderTexture.height), 0, 0);
             myTexture2D.Apply();
                     
             // Restoring the GUI
             Camera.main.GetComponent<GUILayer>().enabled = true;
             
             // Reset Camera and Release the RenderTexture
             Camera.main.targetTexture = null;
             RenderTexture.active = null;
             myRenderTexture.Release();
             
             _capture = myTexture2D;
         }
     }