Our new Whirlpool Duet had the same problem after only three months of use. We contacted Whirlpool (instead of Best Buy) since the washer is still under factory warranty. The issue is a "bad pressure switch".
The part number is W10156252
Service company replaced the part yesterday, and the washer is working like normal. Whirlpool nor the service company had any explanation why the part would go bad in such a short time. No charge since the washer is under warranty.
WARNING - There must be a shortage of the part. We were initially told that the part was backordered for 2 to 3 weeks. We even tried to obtain the part through other vendors and got the same time frame. Furious with the potential of being without a brand new washer for 3 weeks, we spent many hours on the phone with Whirlpool trying to expedite the part. After some strong encouragement and moving the issue up the chain of customer service, Whirlpool agreed to pull a part from the factory inventory where the washers are built. The only problem is that nobody could tell us when, or if, the new part would be shipped. Suddenly, the part just arrived by FedEx at our house. In all, our washer was inoperable for 1 week. Be persistent. They will tell you over and over there is nothing they can do.
If you negotiate well, Whirlpool will extend your factory warranty for an additional year.