[200q20v] re: intermittant "brake" warning light

[C1J1Miller at aol.com]

Had a strange intermittant fault yesterday, and again today.

Driving on highway, normal operating temps, about 70 mph.  "BRAKE" warning 
light glows, goes off, glows, goes off...
Accelerating seems to shut it off; braking has no real effect, and it is very 
intermittant.  Plenty of assist at low speeds, ABS doesn't light up "BRAKE", 
etc.

When I start up after the car sits overnight or over a weekend, the light 
stays on for several seconds, then goes out (and stays out).

How does the power assist pump work... I had thought that 3-4000 rpm engine 
speed would give max assist, so it would appear unlikely that I'm generating 
insufficient assist.  After all, the light is flickering while I'm not using 
the brakes or turning.

Checked the brake fluid level; appears fine, but I'll check it again in 
daylight and perhaps top it off.
Thoughts?
Chris