See Fix the "Could not initialize the application's security component" error message

I tried all these, but it still gives the same error. cert8.db doesnt even exist on Firefox 4

That file is an integral part of Firefox. If you can't find it on on your installation, then this is probably the cause of the problem.

Can you check again? It's located here: C:\Documents and Settings\{Username}\Application Data\Mozilla\Firefox\Profiles\xxx123.default (where xxx123 represents the random name of your installation).

Its not in that folder either. I Searched the whole computer by writing cert8.db in the search box in the start menu. That doesnt find it either

Could you make sure you have Windows configured to show file extensions?

Open Windows Explorer, then go to Tools | Folder Options | View. Then checkmark "Show Hidden Files & Folders" and remove the checkmark from "Hide File Extensions for Known File Types".

Then Apply/OK and run a new search for cert8.db

I tried that too.

Well, unless somebody else has a better suggestion, the easiest thing to do to save you a lot of time troubleshooting would be to uninstall/reinstall Firefox. These are the steps to follow to ensure a clean installation:

1. Go to Download Firefox 4.0 and download a fresh installation file to the desktop.
2. Then go to Add/Remove Programs, scroll down to Mozilla Firefox and remove it, choosing to keep your bookmarks, customizations etc., (don't checkmark the box).
3. Then reboot and delete the folder called Mozilla Firefox at this location: C:\Program Files\Mozilla Firefox
4. Finally run the installation file you downloaded.
5. After you complete the installation, go to the Plugins Check page and update those if necessary.

Adobe issued a Zero Day security warning for Flash, Acrobar Reader etc., the other day, so expect a patch for those to be released shortly.

This should bring you to the profile folder:

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder

If the file isn't there and you keep having this problem then try a new profile.

Create a new profile as a test to check if your current profile is causing the problems.
See:

• Basic Troubleshooting: Make a new profile

If that new profile works then you can transfer some files from the old profile to that new profile (be careful not to copy corrupted files)

See:

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Done that too :(