Does cron delete files

Hi There,

yesterday at 10:40 I created a node and attached some files to it. As i still have problems with the upload module (see http://drupal.org/node/203204) I had to change the permissions via FTP after the uploading. I've done that a few times and it always worked well.

Today both images were gone. They didn't appear as attached files on the node and the files within the files folder were deleted. I was quite wondered about that, and started to look in the logs. The node has been accessed several times, since it was created and there were no "page not found" errors until the cron ran (see Attachments).

Node Access: 27. 12. 2:7 - everythings fine
Cron Run: 27. 12. 3:47
Node Access: 27. 12. 5:06 - both images not found.

There haven't been any actions of Admins (which is only me) during that time.
Is there any possibility that the cron does something like that?

Thanks.