ALSO I have tried starting firefox in Safe Mode already and the problem was still there.

This reminds me of an issue on YouTube where Firefox users cannot paste into Comments. Google is using a script to intercept the Paste command (I'm not sure why, maybe to clean up what you're pasting?) and the script seems to be failing. Maybe a similar thing is happening here...

To test this out:

(1) Do other methods of pasting work beside the keyboard shortcut?

For example, right-click>Paste or Edit>Paste (to activate the Edit menu, you can use Alt+e).

(2) If you block sites from detecting the Paste command, does that have any effect? To do that:

(A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(B) In the search box above the list, type or paste clip and pause while the list is filtered

(C) Double-click the dom.event.clipboardevents.enabled preference to switch it from true to false

The reload the page you want to paste into and test again. Any difference?

Note: This will break pasting on some other sites, so I only suggest it for testing.

(1) Do other methods of pasting work beside the keyboard shortcut?

Yes, I said that in my original comment. I can paste if I right click and then click paste, but ctrl+V dosen't work.

(C) Double-click the dom.event.clipboardevents.enabled preference to switch it from true to false

Already set to FALSE

I changed it to TRUE and now it works.

Thanks for your help ^__^

If a command like Ctrl+V to paste isn't working then you can also try the Shift+Insert alternative.

Use keyboard shortcuts if the buttons on the web page or other methods aren't working.

• Copy: Ctrl+C or Ctrl+Insert (Mac: Command + C)
• Paste: Ctrl+V or Shift+Insert (Mac: Command + V)
• Cut: Ctrl+X or Shift+Delete (Mac: Command + X)