Khmer Unicode, Inglês e Microsoft SQL Server 2008 resulta em pontos de interrogação

INSERT INTO dbo.pmd (patient_code, last_name, first_name, age, sex,province, district, commune, village)
VALUES ('0600-075D4-4AC8', N'ៃាំុំឌគៃុំាំឌ', N'ៃគុំដសហគៃុំះកឆញហេឆ', '2008', 'm', '060000', '060400', '060403', '06040304')

DECLARE @khmertest TABLE (
            SomeText nvarchar(50) COLLATE SQL_Latin1_General_CP850_BIN,
            SomeText2 nvarchar(50)
      )

INSERT @khmertest VALUES ('ៃាំុំឌគៃុំាំឌ', 'ៃាំុំឌគៃុំាំឌ')
INSERT @khmertest VALUES (N'ៃាំុំឌគៃុំាំឌ', N'ៃាំុំឌគៃុំាំឌ')

SELECT * FROM @khmertest

SomeText    SomeText2
?????????????   ?????????????
ៃាំុំឌគៃុំាំឌ   ៃាំុំឌគៃុំាំឌ