OK, I am able to repeat the silent block of programs downloaded from Opera 11.01 in the sandbox. Without Run Safer, Stopping the Avast! shields allows the program to execute. I downloaded a zip file, went to explorer, unpacked and tried to execute it. Started to run, then terminated. So I turned off the Avast! shields and it executed normally. Settings are attached. So I tried to remove Opera from the sandbox, and it would not execute then. Discovered Opera.exe had been corrupted in the removal process, so had to go to an image and get another copy to get started again. Sandboxing browsers seems to have some problems???
UPDATE After cleaning up the mess, can't repeat the corrupting of opera.exe but will keep running sandboxed to see if it reoccurs. The file I had problems with seems to just be something avast! doesn't like. It is silently blocked until I turn off the shields, whether downloaded from the Sandbox or normally. Haven't found anything in the logs or reports that explains this.
I'll keep looking.