I am using Firefox Nightly 32.0a1 and all of the sudden I have noticed this problem:
when trying to open the preferences…
Possibly You have the same problem. Fix it.
1) Close Firefox completely (as in all windows).
1) Open ~/.mozilla/firefox/XXXXXXXXXX.default/ where the “XXXXXXXXXX” is a random string.
2) Find and open file prefs.js in your favorite text editor.
3) Find and remove this line:
4) Save the file.
5) Reopen browser and test the preferences window.
There – that fixed it for me.