Several readers (including Jean-Luc Warin, Ed O'Briant and David Perry) report system freezes/crashes occurring immediately after trying to rebuild the desktop with the latest versions of TechTool or TechTool Pro. I can personally confirm that a system freeze happened to me during my otherwise ill-fated attempt (as reported in the previous item) to rebuild the desktop with TechTool 1.1.4. Upon restarting, I further noted that my System and Finder icons were now gone. After trying several fixes - including a clean install of the system software and a further rebuild of the desktop with TechTool Pro (which did work!) - the icons came back.
David Perry claimed that deleting the preferences file for an older version of TechTool Pro seemed to eliminate the crashing problem he was having when trying to use TechTool Pro 1.0.4 to rebuild the desktop.
To be fair, any attempt to rebuild the desktop may cause problems if there is already corruption on the disk. Still, these reports suggest that TechTool itself may be a factor.