LockBits Bitmap R,G,B reading were messed up?

Hi, I am testing the Lockbits function to read a bitmap r,g,b value.
The codes got part of the bitmap information reading correctly but part of them are just messed up (sometime the red were written into blue, or to green).
For instance, i created a bitmap with RGB(12,32,48) filling, when i read it from the following code, it sometimes is just right with a bunch of (48,43,12) reading, but a few times, in the middle of the printing, there would be a (0,0,12), then the rest is all wrong, (position shifted)
I have no idea when this happen and when it doesn't. I tried it with out bitmap and some of them were right some of them had the same problem.
Does someone encounter the same problem before? Why does it happen? Is there a pattern? How should I avoid it?:(

Code:

---

Public Function BytePixel(ByVal strBmp As String) As Byte()

        Try
            Dim pBITMAP As System.Drawing.Bitmap
            Dim pBitmapData As Imaging.BitmapData
            Dim bytRgb() As Byte
            Dim intLength As Integer
            Dim mRect As Rectangle

            'Get bitmap by specific file name
            pBITMAP = System.Drawing.Bitmap.FromFile(strBmp)
            mRect = New Rectangle(0, 0, pBITMAP.Width, pBITMAP.Height)
            'Get bitmap data
            pBitmapData = pBITMAP.LockBits(mRect, ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb)
            'set array dimension, they array index will start from 0
            intLength = 3 * pBITMAP.Height * pBITMAP.Width
            ReDim bytRgb(intLength - 1)
            'move memory from bitmap to the long array
            Copy(pBitmapData.Scan0, bytRgb, 0, intLength)

            pBITMAP.UnlockBits(pBitmapData)

            'return value
            Return bytRgb

            'clean up
            pBITMAP.Dispose()
            mRect = Nothing
            Erase bytRgb
        Catch ex As Exception
            Debug.Print(ex.Message)
            Return Nothing
        End Try

    End Function

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        'Test bitmap
        Dim aryByte() As Byte
        Dim intIndx As Integer

        aryByte = BytePixel("C:\Wylelabs\SampleCodes\VBNET\ByteTest\input\Test.bmp")
        For intIndx = 0 To (aryByte.Length - 1) Step 3
            Debug.Print(aryByte(intIndx) & "," & aryByte(intIndx + 1) & "," & aryByte(intIndx + 2))
            If intIndx = 500 Then Stop
        Next
    End Sub

---