It seems that the base colours of some add-on themes shows, but most of them just shows as a dark grey background for the firefox homepage. It shows the theme on the tab pages and bookmarks and etc, but it just cuts to grey after. I tried: Reinstalling firefox Setting the 'Override the colours specified by the page with your selection above' to 'Never' Went to the troubleshoot mode, which, for some reason, wouldn't let me click anything I reset Firefox It does the same thing with Firefox nightly and other firefox browsers.

Help!!!