C# - Releasing File Handle On Image?

I am saving an image file, then using Image namespace to resize the image.

The problem is that from the point of when image is saved to the system, to the point where image resizing is handled, the file handle seem not to get released right away, giving me error "A generic error occurred in GDI+"

Here is my code:

I am using asyncfileupload ajax control, C# in VS 2008

string filename = System.IO.Path.GetFileName(AsyncFileUpload1.FileName);
AsyncFileUpload1.SaveAs(Server.MapPath("./") + "abc.jpeg");

//File handle seems not get released right away here.

System.Drawing.Image FullsizeImage = System.Drawing.Image.FromFile(Server.MapPath("./") + "abc.jpeg");
System.Drawing.Image NewImage = FullsizeImage.GetThumbnailImage(60, 60, null, IntPtr.Zero);
NewImage.Save(Server.MapPath("./") + "abc.jpeg");