Firefox Problem

[Mangix]

ok yesterday i downloaded a theme called Outlook 2003 Blue from Mozilla's Extension/Theme place. now that i have downloaded it, i cant access my extensions or my themes. does anyone know how to change the theme manually?

edit:i cant access my extensions/themes because when i click it, a blank window appears and on the botton the 4 buttons appear but nothing else. and i am using that theme.