If I have geo-spherical index on "geo" field I can insert the attached document to mongo DB 2.5.1 but when I try to insert collection as

collection.Insert(BsonDocument.Parse(File.ReadAllText("data1.txt")))

I get error MongoDB.Driver.WriteConcernException : WriteConcern detected an error 'Can't extract geo keys from object, malformed geometry?:
at MongoDB.Driver.Operations.InsertOperation.Execute(MongoConnection connection)
at MongoDB.Driver.MongoCollection.InsertBatch(Type nominalType, IEnumerable documents, MongoInsertOptions options)
at MongoDB.Driver.MongoCollection.Insert(Type nominalType, Object document, MongoInsertOptions options)
at Vlad.MongoGeoTests.Test.MiscTests.Test1() in MiscTests.cs: line 74

Why I get error when using the driver when I can insert it directly to mongo 2.5.1