Same issue . . .
It happens to me fairly regularly, but only when browsing the Engadget RSS feed. I look at plenty of other RSS feeds without problems. I have the same experience on two different Macs, both running the latest version of OS 10.4 (10.4.11 now) so I don't think it's a problem with a specific user account. I've reported the problem to Apple multiple times (the post-crash "send report?" dialog).
I'm guessing (just a theory) some posts or combination of posts in the Engadget feed have something in them Safari can't handle and makes it toss its cookies. Since Engadget is a high volume RSS feed, you could have two people using Safari to browse the feed 30 minutes apart and only one may experience the crash. The "offending" post may be skipped by Safari for the late user or at the very least, the post may be much farther down the list.