My 1990 Sovereign (160k miles) has developed a weird problem with the brakes. I'm curious if anyone has seen this problem before. The ABS system has started engaging periodically when the car is sitting at an idle. First time it happened, I was backing down our steep driveway right after starting up in the morning and the brake pedal went to the floor with the standard ABS "shudder". The scary thing was that I had no brake authority as the car rolled down the driveway - the car would not stop. It has been happening more regularly, always stopped and at an idle when my foot is on the brake. First the brake light comes on, then the ABS light. If I take pressure off the brake and then reapply, it stops. Is it perhaps related to brake system pressure? It's never happened any time except at a standstill and low idle. I had the system flushed and refilled about 4 months ago, so it shouldn't be low. Thanks!