Adblock shouldn't give that error. You must've downloaded Adblock from somewhere other than AMO (addons.mozilla.org) or the official site (adblockplus.org)

Anyway, you might want to try Safe Mode to see if you can open it up,

Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that turns off some settings and disables most add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu by clicking on the Restart with Add-ons Disabled... menu item:


If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

Once you get the pop-up, just select "'Start in Safe Mode"

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

If it opens, then it's probably a problem with your extensions. See the article Troubleshooting Firefox in Safe Mode to help relieve this.

I tried to get into the save mode but Firefox still will not come up. The check for the updates on add-on comes up but not Firefox. I have uninstalled the program and reinstalled and still I can not get Firefox to come up on the screen. But when I shut down my computer it says it is running. I guess in the back ground what ever that means. I have been using i.e. but that seems to have even more problems. Please help me get Firefox working again