SANDBOX - firefox will be BLACK SCREEN

Dear Sir

I have just re-installed my window 7 on the desktop. However, the firefox will be no repond and BLACK screen when I use the right mouse to click "save as’, the situtation cannot be fixed by RESET SANDBOX. Also, I disable AVAST, the situation still alives. Please help me how to set the sandbox to solve the problem.

With best regards

Allan Chung

The problem has been fixed by install Microsoft Silverlight