I have a 2009 iMac(quad core, 12 gigs of ram), and for the most part it runs fine, except every so often the hard disk just goes crazy. Most things aren't affected by this, but if I am playing any video or sound(regardless of the source, it can be iTunes movies, flash movies, the text to audio voices, whatever), it will stop playing while the hd goes nuts, then resume at the point it would have been at if it hadn't paused(occasionally the video goes all Benny Hill and runs through the video really fast to catch up) I occasionally get kernel: IOSurface: buffer allocation size is zero warnings in my logs, but not always. Someone suggested this could be due to flash, but even with killing all the flash processes the hd still spins like crazy from time to time. I don't think the HD is dying as this has been going on for a while, though it got worse in Lion, and it doesn't sound like a broken disk. Although if this keeps up, the disk might wear out much sooner.... Anyone ever see anything like this? If so, how did you fix it?