This is more of a technical question, so I'm not sure if its right for this forum. However, a couple of things for you to check first.
1: did you reboot after the installation?
2: have you changed any settings on your browser. Its likely that your security settings are refusing to let the flash software run. This may also be true of your firewall software.
3: if this fails, I recommend you do a full virus and spyware check. After this go into your control panel / add remove programs (Windows I'm assuming) and uninstall the flash player. Then reinstall by going directly to adobe's site and getting the latest version from them.
I had something similar once about 18 months ago, and it turned out the site had been hacked and it was trying to get me to download a fake flash which was actually a trojan keylogger.