I have had exactly the same problem. My download now is something like 2 Mb and every time it came up with bad checksum. Tried using a download manager because of length of time the download was taking but will not work. Got around it a few months ago by removing the program and using a download manager to reinstall the complete program but now I'm back to the same problem. Hence it is miles out of date. With Windows Defender is Spybot really needed?