I think the cable is the trick....
If you're talking about the backlight issue then it won't be the cable. A data cable would put it into computer mode straight away.
(See separate threads for descriptions of how power-only cables different from data cables.)
Simon, it could be behaviour that's been changed recently with a firmware upgrade, have you done the webupdater thingy since buying it?
Ah yes, I did. And yesterday I saw this in the release notes for 3.20:
Changes made from version 3.10 to 3.20:
# Backlight setting now saved to configuration and set automatically on power-on.
So it's possible that change has also introduced this behaviour, but I dunno if others are using 3.20 and seeing the same behaviour.