SQL Server 2008 :: Why CDC Returning Insert / Delete When UPDATE A Row In Table

I am experimenting with using CDC to track user changes in our application database. So far I've done the following:

-- ENABLE CDC ON DV_WRP_TEST
USE dv_wrp_test
GO
EXEC sys.sp_cdc_enable_db
GO

-- ENABLE CDC TRACKING ON THE AVA TABLE IN DV_WRP_TEST
USE dv_wrp_test

[Code] ....

The results shown above are what I expect to see. My problem occurs when I use our application to update the same column in the same table. The vb.net application passes a Table Valued Parameter to a stored procedure which updates the table. Below is the creation script for the stored proc:

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

if exists (select * from sysobjects where id = object_id('dbo.spdv_AVAUpdate') and sysstat & 0xf = 4)
drop procedure dbo.spdv_AVAUpdate

[Code] ....

When I look at the results of CDC, instead of operations 3 and 4, I see 1 (DELETE) and 2 (INSERT) for the change that was initiated from the stored procedure:

-- GET CDC RESULTS FOR CHANGES TO AVA TABLE
USE dv_wrp_test
GO
SELECT *
FROM cdc.dbo_AVA_CT
GO

--RESULTS SHOW OPERATION 1 (DELETE) AND 2 (INSERT) INSTEAD OF 3 AND 4
--__$start_lsn__$end_lsn__$seqval__$operation__$update_maskAvaKeyAvaDescAvaArrKeyAvaSAPAppellationID
--0x0031E84F000000740008NULL0x0031E84F00000074000230x02119Test26NULL
--0x0031E84F000000740008NULL0x0031E84F00000074000240x02119Test36NULL
--0x0031E84F00000098000ANULL0x0031E84F00000098000310x0F119Test36NULL
--0x0031E84F00000098000ANULL0x0031E84F00000098000420x0F119Test46NULL

Why this might be happening, and if so, what can be done to correct it? Also, is there any way to get the user id associated with the CDC?