Flash is going to be with us for quite a while. Could you be more specific about how the problem manifests itself. For example, do you get a crash in the video area, or an error message, or simply nothing happens? Does it affect some sites more than others?

If you are using Flashblock - it's broken. Remove it and look for a Click-to-Play add-on, if the default in Firefox doesn't meet your needs.

https://support.mozilla.org/en-US/kb/why-do-i-have-click-activate-plugins

FF 34.0.5 Shockwave Flash 15.0.0.239 - set to "Ask to activate"

Problem is with videos & sites that use Flash animation. Sometimes Flash works, other times it errors. Then I use Chrome to view. Never had a problem with Chrome. Prefer FF to Chrome but will most likely switch.

Next time you get the error, could you make a note of the exact text (or grab a screenshot and post it)?

If it says that the plugin crashed, Firefox may have logged detailed data about the crash that you can share with forum volunteers. Please see the last section of this article about how to extract crash report IDs: Troubleshoot Firefox crashes (closing or quitting unexpectedly).