Clicking noise on braking

What is your question?

Hello. My '97 Olds Cutlass Supreme makes this clicking noise when I step on the brakes. It sounds like it's coming from the master cylinder area behind the dashboard. It makes it when the ABS light is out, just after about a half mile of driving after start up, then the ABS light comes on and the clicking noise stops. If I'm on an exit ramp and the light is out, the clicking noise is like rapid-fire, but soon the ABS light glows and the noise stops. Can someone tell me what gives? Thanks.