From MozillaZine Knowledge Base

This article deals with the causes of the message "Could not initialize the browser's security component. The most likely cause is problems with files in your browser's profile directory. Please check that this directory has no read/write restrictions and your hard disk is not full or close to full. It is recommended that you exit the browser and fix the problem. If you continue to use this browser session, you might see incorrect browser behavior when accessing security features.". For information on other messages received when accessing secure sites, see Error loading secure sites.

Hard drive capacity

Check your hard drive's remaining capacity. To do this on Windows machines:

1. Open My Computer
2. Right click on the C: drive
3. Choose Properties. A dialog will come up.
4. Go to the General tab

If it reports less than 1MB free space, you'll need to make more room.

File permissions

Check the file permissions in your profile folder. The file named cert8.db must not be read-only. To do this on Windows machines:

1. Open your profile folder in Windows Explorer.
2. Right click on the file named cert8.db.
3. Choose Properties. A dialog will come up.
4. Go to the General tab
5. Make sure the "Read-only" checkbox is not checked.
6. Press OK.

Corrupted file

The file cert8.db in your profile folder may have become corrupted. Delete this file while the application (Firefox, SeaMonkey, etc) is closed.[1] To do this on Windows machines:

1. Close the application by choosing File -> Exit.
2. Open your profile folder in Windows Explorer.
3. Click on the file named cert8.db.
4. Press delete.
5. Restart the application. cert8.db will be recreated when you do so.

Non-Latin characters in username

There seems to be a bug with non-Latin (For example Chinese or Russian) characters in your username. There's no fix yet but a workaround is to make another account with a Latin characters only username.

New profile

Create a new profile. Your current profile might be corrupted due to many reasons, such as changes in your system or lack of hard drive space at one point.