Yeah, it is due to the so-called crash protection in Firefox that prevents the browser from crashing too when a plugin does.
Here's a 'trick' that worked for me, but it is not guaranteed to work. This also helps if you have a slow computer and get random flash crashes when loading your deck.
You can turn the crash protection off by doing the following steps:
Type about:config in the address bar.
Press I'll be careful, I promise!
You will see lots of settings and a bar on the top. Type dom there
This will show all the strings that contain the word dom. Find the following 3 strings and set their values to what I underlined:
dom.ipc.plugins.enabled false
dom.ipc.plugins.timeoutSecs -1
dom.max_script_run_time 0
Restart your browser, just in case.
This fixed the issue for me, but not sure about others. I also don't know how it works in older versions (I have 4.13), but I hope this helps someone.
Alternatively you can simply switch to Chrome.