1999 Taurus - weird happenings

I have been having an intermittant problem with my 1999 Taurus. While I am driving, the windshield wipers will come on, the dash lights (ABS, seatbelts, etc) come on, the clock defaults to 12:00 and, sometimes, the engine stalls. When it does stall it starts right up. I took it to my mechanic today to have a diganostic on the charging and electrical systems. Everything checks out perfectly. They drove it 25 miles but, of course, nothing happened. I have gone as long as 2 months with it not happening but in the last five days it has happened 4-5 times. Does anybody have any ideas??

I suspect that you have a loose ground somewhere under the dash.