Car does not go correctly - Torque converter doesn't grab right from stop

I have noticed this today and I think it might be getting worse. My trans will engage all gears and hold them, but when I shift into Reverse and push on the gas, or accelerate from a stop, the Torque Converter doesn't seem to grab right (the engine revs up a little before it seems to somewhat abruptly catch and make the car start moving). On wet pavement this evening I stopped the car, made sure it had gone into first gear, and then floored it and made the wheels spin while going straight ahead (I've tried it many times before since owning the car, and the wheels had NEVER spun out). The engine doesn't exactly rev up very high, maybe just a little bit but it's not that smooth action any more. What happened? How can this be fixed? I've got the trans under warranty, so at least dollars won't be a problem. But I still have to drive to work everyday...