I spent over an hour re-installing iChat AV on my G5 iMac desktop--which was a lot more complicated than I had expected it to be. The application had been crashing every time I started it up the last month or two (though it worked fine on my iBook). The solution was to use a program called Pacifist to extract some support folders from the Tiger installation DVD and re-install them on my hard drive--a process I had to learn about from a Mac forum on the Internet. By the way, technical help on the Web is an encouraging affirmation of human nature: there are clearly some very conscientious (and smart) people who go out of their way to provide technological solutions to others of us who may be less computer-savvy.