By default, Flash 11.3 and higher will spin up a lot of distinct processes. You should be able to get quite a cacophony going.

Have you ever done any troubleshooting that involves changing how Firefox works with plugin-container.exe or the Flash player's protected mode?

Often it is helpful to disable hardware graphics acceleration in Firefox and in Flash:

(A) In Firefox, un-check the box here and restart:

orange Firefox button (or Tools menu) > Options > Advanced > General > "Use hardware acceleration when available"

(B) In Flash, see this support article from Adobe: http://helpx.adobe.com/flash-player/kb/video-playback-issues.html#main_Solve_video_playback_issues

Unrelated, but you can remove the Java Console extensions unless you are a Java developer (and even then, you probably don't need the old ones):

orange Firefox button (or Tools menu) > Add-ons > Extensions category

I have disabled it in flash and firefox, and also removed Java Console, and nothing works. Also, if I try to download any plugin updates, it tells me no action list found or internet settings prevent me from downloading. Does this have to do with anything? It did not happen yesterday.

Could you also try Firefox's Safe Mode? That's a standard diagnostic tool to bypass interference by extensions (and some custom settings). More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using

Help > Restart with Add-ons Disabled

In the dialog, click "Start in Safe Mode" (not Reset)

Safe mode does not automatically disable plugins. If you want to rule those out as well, other than Shockwave Flash, of course, you can disable them here:

orange Firefox button (or Tools menu) > Add-ons > Plugins category

Any difference?

I'm not sure about your plugin update issue. Are you using the Plugin Check page or the "gear" icon > "Check for Updates"?

I used plugin check for Java, and I went to the Adobe Flash download page for flash. The problem still happens in Safe Mode as well. Update: I don't know what was going on with my computer, but I can now update plugins. I've updated Flash and Java and the same thing is still happening with the flash and tabs.