For some reason I cannot use new tabs, clicking on the new tab button does nothing. the only way I can open a new tab is by dragging a link onto the tab, otherwise the new tab will now open, how do I fix?

That can a problem with the Ask.com toolbar (Tools > Add-ons > Extensions)

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

i had this problem, i went into the "add-ons" and uninstalled "ask.com" then in the settings add/uninstall programs also uninstalled ask.com. my "new tab" is working again