RIM has updated the BlackBerry PlayBook Operating System again tonight. The update brings the OS to version 188.8.131.528. The update addresses some issues that users were having with keeping contacts and calendars loaded up on their PlayBook. There are a few other minor fixes and improvements, but nothing notable. This update is for the WiFi-only version of the PlayBook. 4G LTE PlayBooks will be updated by carriers as the updates are approved.