The Bitdefender removal tool (referred to above) will likely fix your problem but in the event the problem persists you could try clearing FireFox Cache, Cookies etc.
Assuming you have a recent version of Firefox, click on the “Open menu” button (upper-right corner of browser) and Click on “History” (you may have placed “History” in your toolbar in that case just click on “History” on the icon on toolbar).
Click on “Clear Recent History…” You have a choice to select a time-range to clear, if the problem has been occurring recently you could try selecting “Today” otherwise select “Everything”. Expand “Details” if you need to then select what you want to clear. Unless you really need cookies badly it’s best to select all the choices (you may have to select cookies anyway). Click on “Clear Now” and see if this helps.
