In 3-quart saucepan, cook rice in water as directed on package. Spread rice in 13x9-inch baking dish, cover with plastic wrap and refrigerate for 1 hour or until completely cool.
Meanwhile, in small microwavable bowl, mix vinegar, sugar and salt. Microwave 20 to 30 seconds; whisk until sugar is dissolved. Stir in gingerroot.
In large bowl, toss cooled rice with vinegar mixture. Stir in cucumbers, carrots, green onions and crabmeat; mix well. Top with avocado.