From MozillaZine Knowledge Base

If Firefox or Mozilla Suite/SeaMonkey fails to start then this article may help. (If it starts up but won't load any web pages, then read this article. If it starts but your bookmarks or other settings are gone, read this article.)

Profile locked

One of the following messages can appear when you start your Mozilla browser, if the profile is inaccessible or "locked":

• Profile in Use: The Profile Manager appears along with a message that the selected profile is already "in use" when you attempt to start your Mozilla browser
• Close Firefox: A "Close Firefox" box appears in Firefox 1.5 or above, with one of these messages [1]:
  • "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system."
  • "A copy of Firefox is already open. Only one copy of Firefox can be open at a time."

Ending the browser process or restarting the system will normally unlock the profile. If not, see this article article for further instructions.

Firefox will not start after installing or updating McAfee SiteAdvisor

Firefox may fail to open after installing or updating the McAfee SiteAdvisor Firefox extension [2] or after an update to McAfee software that includes the SiteAdvisor component [3]. According to this SiteAdvisor support article, the problem occurs because of a conflict between SiteAdvisor and automatic proxy configuration scripts in Firefox. Either end the firefox process that remains in memory, start Firefox in Safe Mode and uninstall the SiteAdvisor extension from the Tools -> Extensions window or follow the workaround given in the SiteAdvisor support article. If SiteAdvisor is installed as part of a McAfee software package such as McAfee Internet Security Suite, you can selectively remove just the SiteAdvisor component using the McAfee uninstaller, e.g., via Windows Add/Remove programs. [4].

Windows-specific problems

Firefox does not start after installing the WinAmp Toolbar

Firefox may not start after installing the WinAmp media player, if the toolbar option is selected during installation. [5] [6] You will need to Start Firefox in Safe Mode then uninstall the WinAmp Toolbar via the Firefox Add-ons manager ("Tools -> Addons -> Extensions").

Application fails to start because js3250.dll or other program files are missing

If you see message, This application has failed to start because js3250.dll was not found. Re-installing the application may fix this problem. you must reinstall Firefox (or other Mozilla browser) and check your system for malware. See the article Application fails to start because js3250.dll was not found for more information.

"The program must close to allow a previous installation attempt to complete. Please restart." on Vista

If you are receiving this message when attempting to start Firefox and a restart has no effect, delete the “xpicleanup.dat” file, located in the C:\Users\<username>\AppData\Local\VirtualStore\Program Files\Mozilla Firefox folder. If you have problems finding or deleting this file, follow these steps:

1. Restart your system, or if you know how, terminate all Firefox and xpicleanup processes with Task Manager.
2. Go to "Start -> Start Search" and type in %APPDATA%.
3. From there, navigate to Local\VirtualStore\Program Files\Mozilla Firefox
4. Delete the file "xpicleanup.dat".

You should now be able to start Firefox. [7] [8]

If the problem persists, restart the system or use Task Manager again, then delete the "xpicleanup.exe" file in the Firefox installation directory (usually C:\Program Files\Mozilla Firefox). [9]

"Error opening file for writing..." on Vista

Firefox may require you to be logged in as an administrator. As a workaround, to launch Firefox, right-click the icon and choose "Run As Administrator".[10][11]

Mozilla Suite or SeaMonkey fails to start

If you've tried running the mozilla.EXE or seamonkey.EXE file directly and you also tried running the Profile Manager, without success, the problem is located within Gecko Runtime Environment (GRE), which means you'll have to reinstall Mozilla Suite or SeaMonkey so that new GRE files are created. Solution:

• Download the Mozilla Suite or SeaMonkey offline installer but do not install it yet.
• Uninstall Mozilla Suite or SeaMonkey using Control Panel, Add/Remove Programs (if both are installed, uninstall both).
• Restart the computer.
• (Mozilla Suite or SeaMonkey 1.0.x) Delete the C:\Program Files\Common Files\mozilla.org\GRE\ folder ....THIS IS IMPORTANT!
• Delete the leftover \Program Files\mozilla.org\Mozilla or \Program Files\mozilla.org\SeaMonkey folder if it exists, and all its contents (save your Plugins folder, if you wish, to a backup location).
• With your antivirus program disabled and all other programs closed, reinstall Mozilla Suite or SeaMonkey.

Ref: ilias.ca (Related bug reports: bug 195600 and bug 211694).

Linux-specific problems

Ownership

If you used "sudo" to install Firefox and it starts at the end of the install process and runs when you log in as root but fails to run as a normal user, then check the ownership of "$HOME/.mozilla" and subdirectories. The symptoms are that you won't get any error messages, and Firefox will exit with a value of 1. The ownership of "$HOME/.mozilla" and subdirectories may be set to "root:root", and you will need to execute

chown -R <username>:<usergroup> $HOME/.mozilla

at the command line to get Firefox to work (Firefox 1.0.x).

Similarly other users on the system may need their ".mozilla" folder 's permissions changed using "chown" as shown above.

Fedora 4 libstdc++

When you run from the console window the command /{path to download location}/firefox/firefox you may see

/usr/local/firefox/firefox-bin: error while loading shared libraries: 
libstdc++.so.5: cannot open shared object file: No such file or directories

On Fedora 4, you need to install libstdc++ by running yum install /usr/lib/libstdc++.so.5. After running this, rpm -qf /usr/lib/libstdc++.so.5 should print compat-libstdc++-33-3.2.3-47.fc4.

"/lib/i686/libc.so.6: version 'GLIBC_2.3' not found required by /{path to download location}/firefox/libxpcom.core.so"

If you see

/lib/i686/libc.so.6: version 'GLIBC_2.3' not found required by /{path to download location}/firefox/libxpcom.core.so

or something similar when starting Firefox, then the library is not new enough to support Firefox 1.5 and possibly previous versions. Updating GLIBC is not advised as other applications depend upon it. If possible, migrate to a newer Linux distribution with an updated version of GLIBC.

Other solutions

Perform the standard diagnostic.