Hi
I used SD to make a full backup to a Mac OS Extended (Journaled) partition on an external USB 2.0 drive attached to my Intel iMac.
Everything went fine so I restarted with the Option key held down and selected the backup drive, but then the grey apple turned into a "prohibitory sign" as shown here:
http://docs.info.apple.com/article.html?artnum=106805
So I rebooted in the original drive, ran Disk Utility to verify the external drive - and it said everything was fine, no repair necessary.
Then instead of doing a restart, I did a full shutdown, powered everything down including the external drive, and then a startup - then I was able to boot into the backup drive no problem, and it seemed to work perfectly!
However, it's worrying that it wouldn't boot the first time.... has anyone seen this before, or know why it might happen? Or am I worrying too much ;-)
nylon