After being put into drive or reverse, the car stalls. It starts and runs, but can't be driven.

While driving the other day, the car seemed like it wanted to stall. I pulled it over, and as soon as it idled for a few seconds, it stalled. I put it in park, turned the car off, waited a few seconds, and started it up. No problems. I waited about a minute to put it in drive, no problems yet either. As soon as I put it in drive, it puttered for a few seconds and then stalled. I waited a minute or so, then tried again with the same results. I've been told it may be the O2 sensor or another sensor of some sort, and I've read that it could be the crankshaft position sensor. Since it starts, that ruled out the CPS. Any idea of what the problem could be?