Please always add more info like the OS and the browser etc. when you raise queries in forums as it will help us provide the best solution for you.
Can you check out the solutions listed in the following:
http://helpx.adobe.com/flash-player/kb/installation-problems-flash-player-windows.html (for Windows) or http://helpx.adobe.com/flash-player/kb/installation-problems-flash-player-mac.html (For Mac) for the appropriate solution.
Hope the above helps.