WordPress 3.1 not autoupdating

For the sake of this not haunting unanswered questions…

WordPress tries its best to deal with filesystem/permission issues when updating and requests access credentials if necessary.

So many issues in this department are more likely to be caused by hosting configuration, rather than WP itself. In this specific case PHP safe mode was causing issues, which is not suprising given that it is deprecated feature, discouraged to be used by PHP developers.