Please describe the problem:
If you apply a effect that takes long time,and meanwhile it process, you open 
another effect and make the second effect to apply on the same image (layer), 
the image will be processed same time by both effects and will trash (destrpoy) 
the image. 

Steps to reproduce:
1. Open a big image (eg. 1600x1200) 
2. start to do a Whirl and Pinch effect on image. Imediately after you start 
this, start another effect (like Hurl or Sharpen). You must be sure that the 
second effect starts before first effect finishes the processing. I noticed 
that the second effect starts slowly, but it starts before the first effect 
finishes 
3. You will notice that the progress bar appears for both effects 
4. The image will be become trashed 
 

Actual results:
It seems that the first effect doesnt lock the image (layer) in order to be 
safe for the second effect to be applied. 

Expected results:
I expected to be impossible to run the second effect before the first effet 
finishes. 

Does this happen every time?
I think most time.. 

Other information:
Please notice that the second effect start slowly if the first effect is 
working.