Atmos .Net API: ReadObject after UpdateObject throws exception

Following code snippet throws exception on size if ReadObject is called after UpdateObject. It works fine if ReadObject is called after CreateObject. I tried passing null as well as new Extent(-1,-1) in UpdateObject for Extent parameter. Still go the same error. Any ideas?

                //Update

                byte[] arr = File.ReadAllBytes(@"C:\Users\Public\Pictures\foo.bmp");

                api.UpdateObject(path, null, null, null, arr, null);

                //Read after update

                retval = api.ReadObject(path, new Extent(-1, -1), null);

                File.WriteAllBytes(@"c:\temp\bar.bmp", retval);