>(1) I think you need to set a breakpoint on this and see what's the length of toByte
>
>(2) I have no idea why you are using System.Threading.Interlocked.Increment()

I have adjusted to this to remove the Interlocked. This came from an example on the Internet.

    ' Convert from byte to hexadecimal
    ' expO1 Byte
    Public Function ByteToHexadecimal(ByVal toByte As Byte()) As Boolean
        Dim llOK As Boolean = False
        Dim lnCounter As Integer = 0
        Dim lnLength As Integer = 0
        Dim loStringBuilder As StringBuilder = Nothing

        ' Reset the value
        cString = ""

        ' Initialization
        lnCounter = 0
        lnLength = toByte.Length

        ' The hexadecimal presentation is twice the size of the byte array, we have to multiply by 2
        loStringBuilder = New StringBuilder(lnLength * 2)

        Try

            ' For each byte
            For lnCounter = 0 To lnLength - 1
                loStringBuilder.AppendFormat("{0:X2}", toByte(lnCounter))
            Next

            llOK = True

        Catch loError As Exception
            cMessage = loError.Message
        End Try

        ' Initialization
        cString = loStringBuilder.ToString

        Return llOK
    End Function

However, this is just an adjustment to remove the Interlock. If I would cut the For/Next counter in half, this would work when I go from MD5 to string conversion but would cut in half the value stored in Binary(16).