Unable to access drop down boxes

Not sure if its only me but lately on firefox I am unable to access the drop down boxes that appear when you mouse over the bar that contains activity stream to quick links , the drop down box appears but it seems there is a blank line between the tool bar and the drop box, as soon as you move down from the tool bar the drop box dissapears (like its not linked) seems a space between the two sections ,seems to be the same on all the pages I tried :) Just a heads up ,might be my browser . Cheers ~ John