For other users with this issue, here is specifically what I did. I can’t guarantee it will work for everyone, but it seems to have corrected it for me at least:
gksu gedit /var/www/fog/management/includes/tasks.confirm.include.php
Search Menu > Replace
Search for: &$tmp
Replace with: $tmp
Replace All (there were somewhere around twenty instances)
Save
Close
Then try to schedule your upload task again.