Recently, I was asked to set up a web site for a church; since I didn't want to spend days doing it, I decided to try iWeb.
Things worked well until I updated to 10.6.2. Suddenly, iWeb was crashing on startup, without fail. Fortunately, someone on the Apple forums figured out a work-around.
If you've been getting crashes with iWeb or Pages that blame the SFWordProcessing Plug In, try using Font Book to disable the font named Hoefler. Even though Font Book insists the font is valid, it appears to be triggering the crash.
Once the font is disabled, you will be able to launch iWeb (and Pages) again without crashing -- although all occurrences of the Hoefler font will be rendered incorrectly.
See this discussion (and many others) for more details.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20091111080915220