WINCODEC_ERR_WIN32ERROR 0x88982F94 when calling IWICComponentFactory.CreateBitmapFromMemory

I'm getting the following error when calling IWICComponentFactory.CreateBitmapFromMemory and passing it a pointer to Scan0 of a 32bppArgb GDI+ bitmap

WINCODEC_ERR_WIN32ERROR
0x88982F94
Windows Codecs received an error from the Win32 system.

IWICComponentFactory interface decl:

    new IWICBitmap CreateBitmapFromMemory(
        uint uiWidth,
        uint uiHeight,
        [MarshalAs(UnmanagedType.LPStruct)] 
        Guid pixelFormat,
        uint cbStride,
        uint cbBufferSize,
        [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 5)] 
        byte[] pbBuffer
        );

    new IWICBitmap CreateBitmapFromMemory(
        uint uiWidth,
        uint uiHeight,
        [MarshalAs(UnmanagedType.LPStruct)] 
        Guid pixelFormat,
        uint cbStride,
        uint cbBufferSize,
        IntPtr pbBuffer
        );

Full code:

    public static IWICBitmap ToWic(IWICComponentFactory factory, Bitmap bit) {
        BitmapData bd = bit.LockBits(new Rectangle(0, 0, bit.Width, bit.Height),
                    ImageLockMode.ReadOnly, bit.PixelFormat);
        IWICBitmap b = null;
        try {
            //Create WIC bitmap directly from unmanaged memory
            b = factory.CreateBitmapFromMemory((uint)bit.Width, (uint)bit.Height, 
             ConversionUtils.FromPixelFormat(bit.PixelFormat), (uint)bd.Stride, 
             (uint)(bd.Stride * bd.Height), bd.Scan0);
            return b;
        } finally {
            bit.UnlockBits(bd);
        }
    }

Width, Height, buffer size, format GUID, and scan size all seem correct. I can't figure out why this is happening (there are no google results for the error code or message

This isn't an answer as to why the original code doesn't work - but it's a workaround. Using IWICImagingFactory_CreateBitmapFromMemory_Proxy , everything works fine. But why didn't the original work as it's supposed to? And why the _Proxy methods with near-identical signatures?

[DllImport("WindowsCodecs.dll", EntryPoint = "IWICImagingFactory_CreateBitmapFromMemory_Proxy")]
internal static extern int CreateBitmapFromMemory(IWICComponentFactory factory, uint width, uint height, ref Guid pixelFormatGuid, uint stride, uint cbBufferSize, IntPtr pvPixels, out IWICBitmap ppIBitmap);


public static IWICBitmap ToWic(IWICComponentFactory factory, Bitmap bit) {
    Guid pixelFormat = ConversionUtils.FromPixelFormat(bit.PixelFormat);
    if (pixelFormat == Guid.Empty) throw new NotSupportedException("PixelFormat " + bit.PixelFormat.ToString() + " not supported.");
    BitmapData bd = bit.LockBits(new Rectangle(0, 0, bit.Width, bit.Height), ImageLockMode.ReadOnly, bit.PixelFormat);
    IWICBitmap b = null;
    try {
            //Create WIC bitmap directly from unmanaged memory
        long result = CreateBitmapFromMemory(factory, (uint)bit.Width, 
 (uint)bit.Height,  ref pixelFormat, (uint)bd.Stride, 
 (uint)(bd.Stride * bd.Height), bd.Scan0, out b);

        if (result == 0x80070057) throw new ArgumentException();
        if (result < 0) throw new Exception("HRESULT " + result);
        return b;
    } finally {
        bit.UnlockBits(bd);
    }
}

For reference, here is the COM method and here is the proxy method. Both use [IN] BYTE *pbBuffer.