Which is u'r operating system?
If it's Windows, could you please try this workaround: http://helpx.adobe.com/flash-player/kb/installation-problems-flash-player-windows.html#Ins tall_in_a_firewall_proxy_server_environment
I have done a clean install of flash player, gone through all of the checklists, checked my system for compatibility, I've done this 15 times tonight and I cannot get it to finish the install.
I see that lots of other people are having the problem and there doesn't seem to be a good answer that I have seen. PLEASE, sometone solve this for us!!
This kind of problem is often caused by your antivirus application. Most AV these days have all kinds of additional scanners built in which spring into life as soon as you try to install, or update a program. This interferes with the installation process which ultimately causes it to fail at a certain point.
What you need to do to ensure a successful installation is disable these scanners which are usually referred to as 'Shields' by the AV program. If you're using AVAST, you should be able to see an small round orange icon in your systray. Right click that and go to "AVAST Shields Control". Choose to disable all shields for one hour and then proceed with the Flash installation.
If your not using AVAST, but another antivirus app, consult this list to determine how to disable the shields temporarily: http://www.bleepingcomputer.com/forums/topic114351.html
I would also advise you to uninstall your current version of Flash before you install the latest version to ensure a clean install. You can download the uninstaller from here: http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html (Don't forget to disable those shields before you run it!)
That link I gave you Lisa is not a good one. Sorry about that. Please download the full installer from here: http://helpx.adobe.com/flash-player/kb/installation-problems-flash-player-windows.html#Try _more_solutions
It's listed in the second paragraph called "Install in a firewall proxy server environment "
Xircal: welcome back from your holidays!
You can link directly to the full installers by http://helpx.adobe.com/flash-player/kb/installation-problems-flash-player-windows.html#Ins tall_in_a_firewall_proxy_server_environment