While the Flash Player is running, you will not be able to see anything on the screen. This is because of the malware or spyware infections. This malicious software will alter the performance of both hardware and software. In order to remove the attacks of malicious programs, you need to install good and efficient antimalware or antispyware program, like Spyware Doctor. By regularly updating the antispyware program, you can detect the new malicious program. Also, if the firewall is blocking the Flash Player you will not be able to access the sites that require Flash support.
Get more information to fix flash player problems in windows 7 :http://windows7.iyogi.com/features/windows-7-flash-player-problem/
Hope this helps you.