I've been using a popular complete Firefox theme called FT DeepDark for more than a year without any problems, but since the update to Firefox 45 I can't find a way how to enable it. It is listed in my addons list but there isn't any disable/enable button by it, unlike at other themes. Uninstalling (with a restart each time I was prompted to) and trying various newest versions of the addon from the beta-compatible version list didn't help. Other, simple themes, work just fine. I've contacted the author of the theme but he advised me to try Mozilla support communities, because the theme seems to work for everyone else because nobody has reported this problem so far. Disabling all addons and enabling only the theme didn't help and neither did disabling hardware acceleration. I also haven't changed anything in my settings or addons after or shortly before the 44 - 45 beta upgrade, which introduced the issue. I've even tried uninstalling Firefox and getting a 64bit version this time, but it didn't help me either. I'm on the newest Firefox Beta 45 version since it released (64bit now), Windows 8 Pro 64bit. The theme can be found here: https://addons.mozilla.org/en-US/firefox/addon/ft-deepdark/