Firefox Instructions:
Click here to uninstall
Flash 10.1 first. When the page loads click the link that says "uninstall_flash_player.exe" to download it.
When you click on that link it will ask you to save the file. Click SAVE.
Once the download completes Firefox's downloads window will open up. If it doesn't open up automatically you can open it yourself by going to the Tools menu and choosing Downloads (alternatively you can also press CTRL-J).
Once the download box is open, the first thing in the list should be the uninstall_flash_player.exe file that you just downloaded. Right-click on it and choose Open.
This will run the program and uninstall Flash 10.1 Be sure to follow any instructions on the screen during the uninstall process. You will probably need to close your browser to complete the uninstall.
When the uninstall is completed, reload firefox and visit the link here.
Scroll down to the Archived Versions section and click the very first link for Flash Player 10 (157MB). When you click to download the player file a box will pop up once again asking you to save it or open it, choose the SAVE option again.
The 2nd download will take a few extra minutes depending on your connection speed. Once the 2nd download completes just open up your Downloads window like you did before and locate the Flash Player 10 file in your download list (it should be right at the top of the list again and it should be listed as fp10_archive.zip).
Right-click on the new download and choose OPEN.
When you open the 2nd download a window will pop up that contains a single folder named "fp10_archive". Double-click on that folder to go into it.
Look for the folder named "10r45_2" and double-click once again to go into it.
Look for the file named "10r45_2_win.exe" and double click it to install a fresh copy of Flash 10.0
That's all you need to do! Good Luck =)