[Andreas]

Threads (started by this user):
[sql]SELECT forumid, COUNT( threadid ) AS threads FROM thread WHERE postuserid = 1234 GROUP BY forumid ORDER BY forumid ASC LIMIT 0, 30[/sql]

Posts:
[sql]SELECT thread.forumid AS forumid, COUNT( post.postid ) AS posts FROM post LEFT JOIN thread ON ( thread.threadid = post.threadid ) WHERE post.userid = 1234 GROUP BY thread.forumid ORDER BY forumid ASC[/sql]

Another aproach
[sql]
SELECT thread.forumid AS forumid, COUNT( post.postid ) AS posts, SUM(IF(thread.postuserid = 1234 AND thread.firstpostid = post.postid, 1, 0) ) AS threads FROM post LEFT JOIN thread ON ( thread.threadid = post.threadid ) WHERE post.userid = 1234 GROUP BY thread.forumid ORDER BY forumid ASC
[/sql]

This should give you both figures in one query.

I've attached a quick'n'dirty ACP script that might do what you want.