Sounds like it is hanging when you exit and later try to restart Firefox. * How to stop the running Firefox process ** In Task Manager, does firefox.exe show in the '''<u>Processes</u>''' tab? ** See: http://kb.mozillazine.org/Kill_application * What may cause Firefox to hang at exit ** http://support.mozilla.com/en-US/kb/Firefox+hangs ** http://kb.mozillazine.org/Firefox_hangs ** https://support.mozilla.com/en-US/kb/Firefox+is+already+running+but+is+not+responding * You may need to try Firefox Safe Mode ** You may need to use '''Safe Mode''' to locate the problem: http://kb.mozillazine.org/Safe_Mode **Firefox Safe Mode is a diagnostic mode that disables Extensions and some other features of Firefox. If you are using a theme, switch to the DEFAULT theme: Tools > Add-ons > Themes '''<u>before</u>''' starting Safe Mode. When entering Safe Mode, do not check any items on the entry window, just click "Continue in Safe Mode". Test to see if the problem you are experiencing is corrected. ** If the problem does not occur in Safe-mode then disable all of your Extensions and Plug-ins and then try to find which is causing it by enabling '''<u>one at a time</u>''' until the problem reappears. '''<u>You MUST close and restart Firefox after EACH change</u>''' via File > Restart Firefox (on Mac: Firefox > Quit). You can use "Disable all add-ons" on the Safe mode start window. ** See the following for more information *** http://support.mozilla.com/en-US/kb/Troubleshooting+extensions+and+themes *** http://support.mozilla.com/en-US/kb/Troubleshooting+plugins *** http://support.mozilla.com/en-US/kb/Basic+Troubleshooting ---------------------- '''Other issues that need your attention''' The information submitted with your question indicates that you have out of date plugins with known security and stability issues that should be updated. To see the plugins submitted with your question, click "More system details..." to the right of your original question post. You can also see your plugins from the Firefox menu, Tools > Add-ons > Plugins. *Adobe Shockwave for Director Netscape plug-in, version 11.5 **Several versions out of date **'''''Security update released 2011-02-08''''' *Shockwave Flash 10.1 r102 **'''''Security update released 2011-02-08''''' *Next Generation Java Plug-in 1.6.0_23 for Mozilla browsers **'''''Security update released 2011-02-10''''' #'''Check your plugin versions''': http://www.mozilla.com/en-US/plugincheck/ #*'''Note: plugin check page does not have information on all plugin versions''' #'''Update Shockwave for Director''' #*NOTE: this is not the same as Shockwave Flash; this installs the Shockwave Player. #*Use Firefox to download and SAVE the installer to your hard drive from the link in the article below (Desktop is a good place so you can find it). #*When the download is complete, exit Firefox (File > Exit) #*locate and double-click in the installer you just downloaded, let the install complete. #*Restart Firefox and check your plugins again. #*'''<u>Download link and more information</u>''': http://support.mozilla.com/en-US/kb/Using+the+Shockwave+plugin+with+Firefox #'''Update the [[Managing the Flash plugin|Flash]] plugin''' to the latest version. #*Download and SAVE to your Desktop so you can find the installer later #*If you do not have the current version, click on the "Player Download Center" link on the "'''Download and information'''" or "'''Download Manual installers'''" below #*After download is complete, exit Firefox #*Click on the installer you just downloaded and install #**Windows 7 and Vista: may need to right-click the installer and choose "Run as Administrator" #*Start Firefox and check your version again or test the installation by going back to the download link below #*'''Download and information''': http://www.adobe.com/software/flash/about/ #**Use Firefox to go to the above site to update the Firefox plugin (will also install plugin for most other browsers; except IE) #**Use IE to go to the above site to update the IE ActiveX #*'''Download Manual installers'''. #**http://kb2.adobe.com/cps/191/tn_19166.html#main_ManualInstaller #**Note separate links for: #***Plugin for Firefox and most other browsers #***ActiveX for IE #'''Update the [[Java]] plugin''' to the latest version. #*Download site: http://www.oracle.com/technetwork/java/javase/downloads/index.html (Java Platform: Download JRE) #*Also see "Manual Update" in this article to update from the Java Control Panel in Windows Control Panel: http://support.mozilla.com/en-US/kb/Using+the+Java+plugin+with+Firefox#Updates #* Removing old versions (if needed): http://www.java.com/en/download/faq/remove_olderversions.xml #* Remove multiple Java Console extensions (if needed): http://kb.mozillazine.org #*Java Test: http://www.java.com/en/download/help/testvm.xml

I had the same problem and determined it was the Skype add on causing the issue. I disabled the add-on and now it works fine.