Download the flash remover tool
] to uninstall the 10.x version and then install the old one using the typical installer.
This should work for you.
I don't know if your problem is that:
A) Your app is not suitable/compatible for the newest flash version.
B) You have a problem in the last flash installation.
If your problem is the A option then my soltution will help, but of course this sounds as you will have problems sooner or later and then I'd go for the Dave Kreskoviak proposal.
If your problem is the B option... then trust me as I've been there, I hope you'll be lucky as it is a really PITA to remove a bad flash installation and getting it to work again.