Can you give us more information? What do you want to do? What is the program doing instead? What options have you set? Do you have any add-ons that also program options for tabs?

Under 'Tools' / 'Options'/'Tabs' I checked the 'Open new window in a new tab instead' but con't opening tabs rather than new window. I did not have this problem with the older versions of Firefox.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check for problems with preferences and rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default value.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences