Going to the Acid3 test the first time works (or at least as well as any engine works with acid3). Going to the site again as the next action, either with new tab, back then forwards or new window, causes Webkit to crash. Using Safari 3 released, there is no problem. First noticed it with nightly build for 22 Feb 08, although cannot guarantee that it was not also present from 18 Feb 08 onwards.
I can duplicate this in nightly r30549, but I wasn't able to in r30267.
*** This bug has been marked as a duplicate of 17471 ***