I'm sorry you're going through this. I suspect you're running into a conflict with our Protected Mode which was introduced in Flash Player 11.4. Please try the troubleshooting steps outlined in this FAQ:
In particular, I'd recommend temporarily disabling protected mode (for troubleshooting purposes only) to see if that addresses the issue.
We'd also like to take a look at your crash logs. Please visit "about:crashes" in Firefox's address bar and copy/paste the recent report links in a forum reply.