I've been booting off an external drive until I can get the suckers to open the iMac and replace a dying hard drive. When I checked Software Update this morning it brought up the OS X 10.6.8 update ...

I realize from the outset this is going to be one of those unsolvable problems because it's so entirely random, but I thought I'd throw it out there in case someone has seen similar behavior. 2009 27" ...