In this ABC News article, NASA reveals that the method used to apply insulating foam to the shuttle's external fuel tank was defective. This caused cracks to develop because of spots where there was no insulation, a failure that resulted in a suitcase-sized piece detaching from the external fuel tank of Columbia and striking it's left wing. This foam strike punched a hole in that wing, which lead to the failure of the heat shield.
Is Microsoft's Windows XP Firewall secure? The old Internet Connection Firewall is changed and updated by Service Pack 2 into the NEW on-by-default Windows Firewall. And according to the article, isn't all it's cracked up to be.