I am hoping to clarify this problem and be referred to the right place for assistance.
PROBLEM: My computer (and 3 friends as well) macbook pro's crash about every 3hrs if connected via wireless. They DO NOT crash if connected via ethernet or bluetooth/usb iphone tethering.
ATTEMPTS TO FIX: completely reinstalled snow leopard from scratch- crashes returned after a few days. Replaced the wireless card and entire display-half of my macbook pro via the Genius Bar - no noticeable change.
It appears that an application places a blocking network call then each application that places a network call after that crashes-- causing the entire system to freeze in ~30 seconds from 1st application crash. This is not a kernel panic-- to restart the machine i am forced to hold down the power button until the machine shuts off. There is nothing odd in the console on restart.
for a more complete explanation please visit
http://ask.metafilter.com/142165/Ugly-OSX-Snow-Leopard-Freeze-at-a-loss
applications usually open during crash: itunes, firefox and adium