The only thing that I can think of would if you were not using DISTINCT in your "Active Member Count" Its possible that your query is just pulling up the total instances where a user did an end user activity, which means users are being counted for every activity they do.
This is the query that I have used with good results:
SELECT jivedw_container.name, COUNT(DISTINCT jivedw_activity_agg_month.user_id)
FROM jivedw_activity_agg_month, jivedw_container, jivedw_month
WHERE jivedw_container.dw_container_id= jivedw_activity_agg_month.dw_container_id
AND jivedw_month.month_of_year=1 --(this is the number of the month)
AND jivedw_month.year =2011
AND jivedw_container.container_type =700 --(for spaces, other container codes can be put here)
GROUP BY jivedw_container.name
Thanks for your reply. Now that I'm on to the next month of reporting, I'm focusing on this again. I'll be checking that Distinct part as well as the query.