Submit your Crash ID here as described in the following article:

• Get help fixing this Crash

Until we take a look at your Crash Reports (which will be fetched by using the Crash ID that i have asked you to post here), see these articles:

• Firefox Crashes
• http://kb.mozillazine.org/Firefox_crashes

Since I can't get on Firefox, I don't have a "crash ID".

Just tried to download 12.0 again. After download, hit "Run". This time I got an Internet Exporer error box with no info. No Firefox icon appears.

Previously, the only error I could read had something to do with a DLL error. Again, no way to get on Firefox.

The 12.0 upgrade has basically locked me out.

1. Did you try the Firefox SafeMode to see if it crashes there?

• You can open the Firefox 4.0+ SafeMode by holding the Shft key when you use the Firefox desktop or Start menu shortcut.
  

Don't select anything right now, just use "Continue in SafeMode."

2. Did you see this in Get help fixing this Crash?

You can't open Firefox because it crashes at startup even in Safe Mode:

   Click the Windows Start button, and select Run... on Windows 2000/XP or press Windows Key + R on Windows Vista/7. Type in "%APPDATA%\Mozilla\Firefox\Crash Reports\submitted" including the quotation marks and click OK.
   In the resulting folder will be a text file for each crash report you have submitted. Using the View 

Download and save the Firefox installer to the desktop and start the installation with a double-click on that desktop icon.
Do not try to run the Firefox installer directly from the IE download.
You may have to disable your anti-virus software temporarily if you keep having problems with downloading the file.

You can find the latest Firefox release in all languages and for all Operating Systems here:

• Firefox 12.0.x: http://www.mozilla.org/en-US/firefox/all.html