Resize Arithmetic operation resulted in an overflow

When trying to upload/save a .gif file I am getting the following error "Arithmetic operation resulted in an overflow.". Here is the code where the error occurs.

                Telerik.Web.UI.ImageEditor.EditableImage img = e.Image;
                
                if (img.Width > 600 && img.Height > 600)
                    img.Resize(600, 600);
                img.Image.Save(sFullPath + sFileName + sExt);

                if (img.Width > 150 && img.Height > 150)
                    img.Resize(150, 150);
                img.Image.Save(sFullPath + sThumbName + sExt);

I added the code to check the size of the image before calling the Resize but it still throws the error. How do I fix this?