I've had this same problem. I changed the oil pressure sensor and it stopped. I've seen it do it one or two more times, but only after driving in the desert in 100+ temperatures.
The oil pressure sensor is located at the rear of the engine, below the spark plug on the passenger side. It's a real b***h to get to.
__________________
Good Luck...
mj
'01 Ford Ranger 3.0 Super Cab, K&N Air, MaxFlow Exhaust, Oversize Tires 
'93 Ford Taurus 3.0 (What a MONEY PIT! Traded it in for the '01 Ranger) 
'87 Ford Ranger 2.3 Super Cab (Owned it for 16 years until some clown T-boned me in it!) 
'92 Ford Aerostar 3.0 (Gave it to Ex in Divorce Settlement) Hehe...
'74 Ford Maverick 250 ci (Great car! Cruised at 110 mph on Autoban! Traded it in for the '87 Ranger)
'66 Ford Mustang 200 ci (Screwed up and SOLD IT!!)  | 
