I’ve just downloaded and installed the latest update for OS X via the Software Update utility. The update requires a system restart which isn’t unexpected. What was unexpected was the second restart in the middle of the reboot sequence.
After my heart resumed something approaching its’ normal rate I did what I should have done in the first place and read the update documentation. If I’d done this I should have spotted the key phrase:
With the Mac OS X 10.4.6 system software update, PowerPC-based Macs will restart twice, instead of once, after the initial installation.
No explanation as to why this was neccessary though.
This was also spotted, with similar cardiac effects, by todays edition of The Register.