The last two updates have each produced a kernel panic after the (forced) reboot. Tiger Cache Cleaner readily diagnosed the reason: the installer program apparently fails to DELETE the old Microsoft Mouse System Preference pane (TCC complains about a duplicate Pref Pane). A safe reboot (hold down the shift key upon reboot) will permit you to delete one or the other.

Before deleting one or the other, you can check the version info by cliicking on the arrow icon in the upper right of the Microsoft Mouse panel, next to the Microsoft IntelliPoint phrase.

I don't have a Microsoft keyboard, so don't know what happens in this case.

Is this Microsoft's first post-Windows Safari gift to Mac owners? :)