statistics not working

When I create a custom member statistic, I noticed that some members weren't included while they did match the inclusion criteria. First notice was that even if the minimal amount of posts was 0 (till -1), users aren't shown if they have 0 posts and sorting is set on 'messages'. When I try to...

I can't see any forum statistics, no matter which timeframe I choose. However, the cronjobs overview tells me that everything seems to be fine, all cronjobs are scheduled to run again within the next 24 hours. Any queues?