Strange alarm behavior, 93 100CS

[John Larson]

Alarm engages when the car is unlocked, disarms when the car is unlocked,
with both the key and the IR.  I have a new actuator/latch assembly at hand,
but don't really want to throw $125 at it if it's not the problem.  Interior
light switch is 6 months old, all else in the latch/lock area appears OK.
Happened suddenly, and hasn't behaved properly since it did, so it's not
intermittent.  Anybody had the locks and alarm out of phase before?  The
fix?  TIA, John