[BirdOPrey5]

#1)

SELECT ipaddress, GROUP_CONCAT(DISTINCT userid) AS userid, GROUP_CONCAT(DISTINCT postid) AS postid
          FROM post
          WHERE dateline > 1335925435 AND userid > 0 AND ipaddress != '' 
          GROUP BY ipaddress
          HAVING COUNT(DISTINCT userid) > 1
          ORDER BY COUNT(DISTINCT userid) DESC
          LIMIT 500;

That is the code for the 7 day look back of the posts table. You will have to put a table prefix in front of "post" if you use them.

#2)

SELECT ipaddress, GROUP_CONCAT(DISTINCT userid) AS userid
          FROM user
          WHERE joindate > 1333938235 AND userid > 0 AND ipaddress != '' 
          GROUP BY ipaddress
          HAVING COUNT(DISTINCT userid) > 1
          ORDER BY COUNT(DISTINCT userid) DESC
          LIMIT 500;

That's the 30 day look back of the User table.

I'm curious if either of these produce any results (return any rows.)?

If they don't, let me know. if they do maybe you can PM me what it returns, you can edit/mess up the IP addresses for privacy if need be.