GrayfoxBeach Ball.
Run hardware tests or reinstall.
neema_tActivity Monitor and Disk Utility are both in my dock and used often, probably more often than most applications I use, to check the permissions, disk and also to make sure that there aren't any unknown processes using up all my RAM. I use MediaLink to serve media to my PS3, one day I checked Activity Monitor to find it had opened several instances of ffmpegx which were maxing out all 6GB of my RAM... I wasn't impressed!