Can you proved an exact description of your problem?
I have the same issues, running the latest versions of Firefox and Flash player 11.7, anything with Flash will instantly crash if it is enabled, I had previously been using 10.3 whilst 11.6 was giving the same issue assuming it would be fixed with 11.7 but it's still not working. I have tried a clean install, turning protected mode on/off and disabling all other plug-ins and addons already, but the only thing that works is using 10.3.
My PC shouldn't have any issues with Flash Players requirements, but here's the specs anyway.
Windows 8, upgraded from 7 but with a clean install.
AMD FX 8350 CPU at stock.
Nvidia GTX 660 GPU with the latest Nvidia 314.22 drivers.
8GB DDR3 1600MHz RAM.
Onboard 7.1 audio controller via external DAC. (Disconnecting DAC and disabling audio drivers makes no difference).
1TB HD 7200RPM with approx 750GB spare yet.
75MBP/s average Download speed, 25MBP/s average up internet connection.