Don't rule out the possibility of a slightly out of spec sender. The oil
pressure sender in my '89 tended to set the buzzer off at a bit higher oil
pressure than it was supposed to until I replaced it, causing exactly the
same symptom.  Also, how long has it been since you changed the oil, and
what is its viscosity?  I've found that the wasserboxers tend to like 20W50,
especially if they have some mileage on them.  (Thicker oil can mean higher
pressure, of course.)  In any case I'd start with an oil change, an oil
pressure check when the engine was nice and hot, perhaps a new sender if
called for, and if all of that fails, even a slight stretch of the oil
pressure relief spring before I started to worry too much.

- Ron Salmon
  The Bus Depot, Inc.
  (215) 234-VWVW
  www.busdepot.com

 I was driving down Interstate 5 heading due south, going about 80 mph, saw
a gas station, decided to exit when at that moment the buzzer went on. Water
temperature wasn't higher than the top of the led itself. I turned the
engine off, and coasted down the road, into the denny's parking lot next to
the gas station. Let it cool, let my mind run wild. Added more than half of
a bottle of gunk. Wasn't low on any fluids. After a few hours, I started, it
ran, and I drove 60/65 mph all the way to Riverside. No problems since then.
Thinking is, oil got hot which made it thin out which caused the oil
pressure to drop. It wasn't that hot that day. Is this just a day in the
life, or is it an omen?