First - don't panic
There are updates which may take several minutes which the Scroll Bar actually 'hangs'
Next - you may need to uninstall the game then re-install (you do not lose your pirates or any information - thats all kept server side and not on your computer) - the odd update sometimes doesn't download correctly.
We also have several MAC users here which can thow in tips when they see this (since I don't own one).