Firefox is not letting me open another tab when I click the 'new tab' button. It says 'done' in the corner, but never opens a new tab.

In past threads, this problem has been linked with the Ask toolbar. [http://support.mozilla.com/en-US/questions/784371 I can't open a new tab anymore; what happened? | Firefox Support Forum | Firefox Help] [http://support.mozilla.com/en-US/questions/788008 New tab button does not work, nor does "Open New Tab" toolbar icon. | Firefox Support Forum | Firefox Help] And several users mentioned a link between Foxit Reader and Ask toolbar: [http://support.mozilla.com/en-US/questions/786427 "Open a new tab" is not working in Firefox 3.6.13 on WindowXP NT | Firefox Support Forum | Firefox Help] [http://support.mozilla.com/en-US/questions/794912 I can't open a new tab | Firefox Support Forum | Firefox Help]