I'll try to get some screenshots together. It only seems to occur when the files are on a remote server and the files are on the larger side (say 25MB per log file). If use small files, it works.
The task is set so that the content to archive is specified on a share, such as "\\server\sharedfolder". It is using a domain admin account as the credentials in the content tab. It compresses the first file, then all the rest are blank.
I think this could be a permissions issue where it is losing it's ability to access the files after the first one. If I use small files it works, large files it does not.
I was able to work around this (I think) in one of two ways. First, I tried using a mapped network drive, and that seemed to work. I then changed the "Visual Cron" service to use a domain account that has access to the share, and now that seems to be working well too.
I'm going to do some more testing...
It seems like a bunch of people on the forums change the service to use a domain account. I think I like that approach since a large number of my tasks are accessing domain resources anyway. Except for having to alter the service anytime an upgrade is done (since it switches back to SYSTEM), is there any downside to running it as a domain account?