2004 Ford Taurus It willn't start after driveing

you drive the car 5 min or 5 hour,but if you turn it off & turn it right back on nothing no sound,but wait about 45 min. it will start but turn it off & back on,nothing.but on the dash the yellow light Low Oil Pressure light up.... the battery was replace in 06-2009 when this problem begin an had no touble starting until 2 days ago 1-23-10. now could a ( Low Pressure Sending Unit)or (Low Pressure Swicth) Keep it from starting. thank you mike V6 3.OL OHV