In a bowl, dissolve gelatin in water. Stir in strawberries, pineapple, bananas and nuts. Pour half of the mixture into a 13x9x2″ dish. Refrigerate for one hour or until set. Set the remaining gelatin mixture aside.
Combine the sour cream, sugar and vanilla; mix well. Spread over the chilled gelatin. Spoon remaining gelatin mixture over top. Chill overnight.