ABS Failure?

Hi all, I just bought a 2001 Prius with 68,000 miles. The ABS and Brake lights are lit up on the dash, and I am experiencing some odd braking indeed....

As far as I can tell, it is not leaking fluid anywhere. I have sufficient braking power for 3-10 seconds, then I seem to lose pressure.

It's like the ABS pump just stops working, the majority of the time it is fine, however if I am sitting at a light I tend to lose pressure in the system.

Like I said though, I also have sufficient braking power for 3-10 seconds... So if I stomp the brakes, it stops immediately.

Another oddity is that when I first get in my car, it feels like my brake pedal has *some* pressure, then it firms right up after 2 seconds of being on the brake pedal.

Any ideas what this could be?? I checked all of the relays and fuses Mr. Wilson provided to check in the last thread "c1256-low-pressure-accumulator-abs-beepabout" about another ABS failure...

Any help is appreciated!!!

FYI I have stopped driving the car because of the brake issue....seems to unsafe for me!