I am running Vista Enterprise and have moved a 4.8 GB zip file to my
Documents folder. Although Vista opens and processes the file fine at first,
at some point during the day, the file turns into a zero-byte file. No
reboots or unusual events took place before the data loss. Nothing
interesting is in the Event Viewer.

This has reoccurred 3-days running. (I recopied the file 3 times). After the
data is lost, the modification date is unchanged from the original file.
Shadow copy shows no “previous versions.” The NTFS partition has 71 GB free.
Another copy of the file (with a .zi_ extension) is not affected. No
third-party zip utilities have been installed.

What could cause the file to become empty? How can I trap this event?
Thanks.