The incrementing is done entirely by your query. If the value is being set then it's being stored fine and the issue is with the query not incrementing correctly. Your query has a subquery inside of a subquery, the first subquery isn't really needed. Try the following.
Code:
UPDATE `#__comprofiler`
SET `cb_member_` = ( SELECT ( `cb_member_` + 1 ) FROM `#__comprofiler` WHERE `cb_member_` > 0 ORDER BY `cb_member_` LIMIT 1 )
WHERE `id` = '[user_id]'
krileon
