When I recently manually archived 1.70d[b].001 (since it had been reported that automated archiving wasn't working), I noticed it seemed to do something (took time, hard drive light, etc.) but when I called up the list of available archives, the most recent one was of "Galactic Civilizations II Dark Avatar (Expansion Pack)_1.50.128", dated 6/7/2007. The actual file name was "Galactic Civilizations II Dark Avatar (Expansion Pack)_1.50.128_06.07.2007.sdc" but the modified date when I looked at the actual Backup folder was today's date (with a creation date of June 20, 2007.
It is my conclusion that the archives are overwriting the most recent archive instead of creating a new file with a new version and date as part of the file name, and this is affecting both automated and manual Archive requests within the Stardock Central user interface. This appears to have been happening since v1.50 and June 2007.