When moving around the config pages of my Billion 7800N I have been getting salmon pink error pages with a 400 Bad Request error message. A quick browse on the Billion forums revealed this to be a problem others are having when browsing the router with FireFox v15.0. I am using Waterfox v15.0, the dedicated 64 bit version of FireFox. I fired up Internet Explorer and browsed the router with no errors at all. So if anyone has this problem the solution sadly is IE until FireFox is fixed.