Hello Bo, I split your comment into a new discussion. Your report is the first one about this specific problem. Add-ons can very well be the case. In your case it's best to click Tools>Add-ons, the go to Extensions and disable all of them manually. Then quit the browser and open a few links from Mail to see if it still crashes.
Thanks, Chris. The problem has seemed to resolve without disabling any Add-ons -- perhaps my Powerbook just needed to get used to the new TFF update. Anyway, as said before, TFF has been a lifesaver for me and my vintage Powerbook - lol - much appreciated for all the great work you are doing in the back room :)