That is because you are not suppose to manually run that file.
You would get that error no matter what version you run.
cron.php is the cron script that is designed to run in the footer of the actual classifieds script.
sendnotice.php is the old server style cron task that is setup through your servers cron task procedure or you can run it manually although running it as a server task is the correct action so it runs when it is suppose to.