Starting Problems 2001 Cougar...

My girlfriend has an 01 cougar, the car has run great since she has had it. This winter she started noticing some difficult starts, the morning i tried to start it it started fine, put it into gear then it immedatly died. so i cranked it for about ten seconds until it started again then all the gauges on the dash maxed out for about 5 seconds then returned to normal (electrical problem?) but once again as soon as i touched the gas it died out. I bought a battery to see if it would help, it did. So I took the car to have the alternator tested, the amp output was weak so i had the alternator rebuilt, she has been riving the car three days without a problem and then this morning same thing, car stalls out when she puts it in gear.

Any ideas, im lost on ford electrical...

thanks
Dallas