This is not behaviour I recall hearing about before. Are you saying th tabs initially open as tabs in a single Window, or is it a case of firefox opening multiple windows when it starts up or everytime you try to open a new tab ?

Have you checked the setting

• Firefox Button -> Options -> | Tabs | [] Open a new Windows in a new tab instead
• even if that does not solve the problem please try the setting and report whether it has any effect does it work as intended ?

If that is not the reason then try safe mode use only the default theme and disable all plugins. Does that help ?

have done what you suggested, as well as trying pinning Apps as tab and no, it has not worked. [Q] Are you saying th tabs initially open as tabs in a single Window. A: Yes. But then the tabs will "disappear" and re-open as a new window.

Did you try disabling all plugins. Try a new profile.

• basic troubleshooting_8-make-a-new-profile

If that fails maybe you need to consider the possibility of malware. Or some interaction with other software.

It is possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox Profile Folder.

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

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

See also:

• http://kb.mozillazine.org/Session_Restore
• http://kb.mozillazine.org/sessionstore.js
• http://kb.mozillazine.org/Multiple_profile_files_created