A common error with the Mozilla Firefox browsing software is the "Firefox is already running error." If you attempt to launch Fire fox and get this error there can be several reasons and possible fixes. This is one of the most frequently reported errors with the Firefox browser. In most cases you can relax, as the fix is easy. If you are on a network and have permission, file location or profile problems causing this error to be generated, then you will need to contact the System Administrator for assistance.

The following issues can cause the "Firefox is Already Running" error:

Firefox was not shut down correctly

If the Firefox browser or your system experienced a crash or unexpected shut down, the Firefox program may close without deleting the profile lock created with each launch. This leaves Firefox running in the background, which you may not see. Normal shut down of the Firefox browser results in the lock file being deleted upon exit.

The fix:

• Access the Task Manager or Process List by pressing “Alt-Ctrl-Delete”.
• Click and highlight the running instance of Firefox.
• Click “End program”
• Re-load Firefox

Firefox 3 Delayed Shutdown

This version of Firefox has a delayed shutdown. If the application is re-launched too quickly, it will generate this error.

The fix:

• Access the Task Manager or Process List
• If it shows an instance of Firefox running, click the program to highlight it.
• Click “End Program”
• Re-launch the Firefox browser

If you are using this version, remember to wait after closing the software or download the latest version of Firefox for free here.

For PC’s on a Network

If your Firefox software is located on a networked or shared system, you may have an incorrect command line argument that is not allowing remote access of the software or you may not have correct permissions assigned.

The fix:

• Contact your administrator and have them resolve these issues.

If the above solutions do not work, reboot your system. This will allow Firefox to re-initialize and should correct any issues that resulted from the last session that generated this error.

In the rare instance that a system reboot does not resolve the problem, you may have corrupted files in the Firefox application. If this is the case, you can re-install the Firefox software, as this will return all settings to the default state.