After I have started the firefox, all the icons become black in colour, I can't click on any buttons or the menu bar and can't type anything in the url box. However, the browser seems to be working cause it can go to the default page.

one more thing, if i press crtl l, i can go inside the url box and type the url, but i can't use the pen/mouse click the url box and type things.

The alt F key and other alt key are also work