Go to 'Database -> Database Management' and rebuild your database cache via 'Rebuild Cache -> Full Cache Rebuild' and see if that resolves the issue. This might take some time if you have a large database and make sure that your computer does not power itself off or go to sleep while it's running or you will need to run it again from the start.
What version of PostgreSQL do you have installed? You should see it displayed in the bottom right of the 'Database -> Database Management' window. Also if you create a new database, set that as active and import the hands there does the same thing happen?
first of all, thank you for trying to help me! Sadly the same problem, stats are still bugged. A friend of mine told me yesterday that he has the exact same problem.