Of further interest:
As one might guess, when multiple extensions are enabled, all of them appear in the "default set."
The cursor need not be moved into the sheet in order to invoke the spinning beachball; there's just a few seconds' delay between the appearance of the sheet and the appearance of the beachball.
If, upon the first relaunch following the crash—the relaunch in which Google fails to load—I choose Customize Toolbar..., no extensions appear and there is no crash. (This is presumably because Safari is relaunched with the previous prefs, the crash having prevented the new (enabled) state of the extension(s) from being written to the relevant plist.) If I now dismiss the sheet by clicking Done...
...Google loads!
Edit: the loading of Google following the dismissal of the sheet turns out to be coincidental. Further investigation confirms that Google will eventually load on that first relauch all by itself; it just takes twenty seconds or so.
Last edited by dkmarsh; 06/12/10 11:53 AM. Reason: Update
