When installing copy-protected software on a Macintosh, be sure that all the extensions are turned off (either turn them off in Extensions Manager, or restart your Mac holding down the "shift" key). Not doing so greatly increases your chances of losing an install authorization!
Corollary to the above tip: If you’re not going to follow our advice on turning off all extensions (which you really should…), at least be sure that you have turned off any virus protection INITs you may be running while installing and authorizing your software.