Highlight your HD icon, hold command key and click "I" key to get info. In the resulting window, click on the padlock at bottom right. Enter your password if asked. Close this window, and you should be A-OK!
The padlock at the lower right-hand corner of the "Get Info" window does not have anything to do with whether a drive is "locked" or not.
The padlock only turns on and off the ability to edit permission information in the "Get Info" window. It does not have any actual effect on the drive itself.
It does seem to produce the same results on my system (padlock icon in lower-left of Finder icon) when the "Locked" box is checked and/or unchecked. +2 internets to you.
Perhaps next time I can, if I have a solution to suggest. In the meantime, I'm still going to operate off of the guise of "no information is better than false information."