DbUpdateConcurrencyException when inserting a single row

I cannot insert a row in the table defined below. I have to conform to the table´s composite primary key. When using Entity Framework to insert a single row into the table, I get a DbUpdateConcurrencyException. Digging a bit deeper into the exception I see "OriginalValues cannot be used for entities in the Added state."

• I am running EF 6.1.3 database first
• My database is a SQl 2008, set in compatiblity mode 2005.

Below is my code for addding the row as well as the table schema.

c# code:

Entities.Entry(new jotch_krdtrans() {Kred = 1, Regdato = DateTime.Now}).State = EntityState.Added;
Entities.SaveChanges();

SQL table schema:

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[jotch_krdtrans](
    [Kred] [decimal](12, 0) NOT NULL,
    [Regdato] [datetime] NOT NULL,
    [Autonum] [decimal](18, 0) IDENTITY(1,1) NOT NULL,
 CONSTRAINT [PK_jotch_krdtrans] PRIMARY KEY CLUSTERED 
(
    [Kred] ASC,
    [Regdato] ASC,
    [Autonum] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

I have tried setting the ProviderManifestToken to "2005" in my edmx-file and this seems to make it work. However I would prefer a more detailed explanation why this makes it work. What changed between 2005 and 2008 in relation to my insert example? I am hoping for a deeper understanding.

Thanks in advance.