When you start Firefox, does it display your home page, or a blank page, or some other unknown page?

If you check the History menu, is Restore Previous Session enabled and does it work?

Could you check for possible overrides to your normal startup in the following places:

• A "user.js" file in your currently active settings folder (Firefox profile folder), as described in this article: How to fix preferences that won't save.

• A web address in your Firefox shortcut (the icon you use to start Firefox). If you right-click the icon > Properties > Shortcut tab, for "Target", you should have the following, no more, no less:

"C:\Program Files (x86)\Mozilla Firefox\firefox.exe"

Make sure that you do not run Firefox in permanent Private Browsing mode (Never remember history).

• https://support.mozilla.org/kb/Private+Browsing

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

There are other things that need your attention.

Your System Details List shows multiple Flash plugins. Shockwave Flash 14.0 r0 Shockwave Flash 12.0 r0 Shockwave Flash 11.9 r900 You can find the installation path of all plugins on the about:plugins page.

• http://kb.mozillazine.org/Issues_related_to_plugins#Identifying_installed_plugins

You can check the Flash player installation folder for multiple Flash player plugins and remove older version(s) of the plugin (NPSWF32) and possibly (re)install the latest Flash player.

• (32 bit Windows) C:\Windows\System32\Macromed\Flash\
• (64 bit Windows) C:\Windows\SysWOW64\Macromed\Flash\