Bitmap.SelectActiveFrame

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Hi everyone, I would like to know if someone have experienced slow issues with Bitmap.SelectActiveFrame in a 64 bit system, or why is the method so much slower in a 64 bit system than in a 32 bit? Here is a sample code that I have used to test:

Bitmap m_bmp = new Bitmap("C:\\01.tif");
String m_Start = DateTime.Now.ToString("hh:mm:ss");
System.Diagnostics.Debug.WriteLine("Started at: " + m_Start);
for (Int32 a = 0; a < 22; a++)
{ m_bmp.SelectActiveFrame(FrameDimension.Page, a); }
String m_Finish = DateTime.Now.ToString("hh:mm:ss");
System.Diagnostics.Debug.WriteLine("Finished at: " + m_Finish.ToString());

The 01.tif file is a black & white image with 1bpp and 23 pages with 300dpi. Test made with Windows7 VS2010 .NetFramework 4.0 32 bit: Less than 1 second. Test made with Windows7 VS2010 .NetFramework 4.0 64 bit: 6 seconds. This is really a lot. Can someone be kind to help me ? Thank you. Best regards.