This may sound daft but worked for a different problem with new client [constant crash on loading world]. Make sure everything PS related has been deleted, apart from your download. Turn off your pc, make cup of tea or go to pub. Fire up your pc, try to install. If you get first part running then update when prompted. After the updater has finished turn pc off again, tea or pub, put shader and textures to medium, untick vbo [esp if running ATI card] in Graphics, then cross fingers and go for it. Good luck, it's worth it.