I download files to an external HD, which isn't always on. But the same occurs when you delete the downloaded files.
It's still in the download list as ready, but it probably checks if the files are in the download dir and if not happily starts downloading again!
And autorar is turned on.
Hmm... not sure if it would happen ALL the time, as my download dir and autorar dir aren't the same (download dir is on my laptop, autorar dir is external).