Uninstall the Ask toolbar and it should work again. There is a compatibility issue with the Ask toolbar and Firefox that prevents new tabs from being opened.

That was it. Thanks for help.

You're welcome

I don't have the Ask tool bar showing up. when i go to 'View' and then 'toolbars' it is there but i don't have it activated. How do i uninstall it? when i click 'open new tab' nothing happens. Thanks for any help

Check the Windows Control panel for the Ask Toolbar - http://about.ask.com/apn/toolbar/docs/default/faq/en/ff/index.html#na4

Also check your list of extensions, you may be able to uninstall it from there - https://support.mozilla.com/kb/Uninstalling+add-ons