It is odd but I know I use firefox and I do have issues playing flower knight girl very similar to what you described but I am able to play aigis fine, it works when I use another internet connection besides my home one on firefox but when I use my home one it only goes to a black screen. So I now play Flower Knight Girl on Internet Explorer, I never found a solution to it.
Whether or not this is the same thing that is happening to you for aigis I do not know.