Hi again ... plugin updated.
I tested a Google Custom Search and I realized what it was about.
The problem with this f** google, is that there is NOT a predictive behavior. Some thumbs-images are generated correctly, while others do not.
I view the issue in my own custom search via publicphoto.org, i searched for articles with recent topic "Galaxy S3" here http://publicphoto.org/google/
And yes, its a random problem.
- I do not know if this will solve the problem,
- we can not know until google regenerate images again.
- I do not even know how often google regenerate images.
P.S. After update do not forget to enter in plugin configuration and use the "Update Options" button. You should not delete the cache.