In 6.70B9 (Win7), I find that I have to reload the group from the disk after I 'Download the Latest Group Update' on a group that is open. or a portion of the headers do not appear. Once reloaded, all headers appear to be there, and some that were being reported as incomplete are shown as completed.
Also, only a couple of times, a download will freeze, even the program seems to be responding. I am also unable to add to the download list. Closing and re-opening the program resumes the download without issue.