A user e-mailed me with a problem. He is using 64bit ColdFusion and recently tried to apply the 8.0.1 update, but kept receiving errors about missing files (including iawin32.dll). ColdFusion Product Manager, Jason Delmore, figured this one out. If 32bit ColdFusion is installed and then the 64bit updater applied, subsequent updates may not work. The solution is to manually uninstall ColdFusion, and then reinstall the 64bit version. This TechNote explains how to manually uninstall ColdFusion. It was written for ColdFusion 6 and 7, but still applies (with version names changed appropriately).
As a note point, all the installs of CF8 64-bit I have done so far went painlessly.