I think it has to do with how your browser remebers authentication, your browser see's that you are going back to the root and because you could access the root folder with either no password or a different password before it uses that and not the one you used to access the restricted folder.
to see if my theory is right
close your browser to clear any cached passwords/users.
goto your hfs and log into the root folder with the user/pass required to access the restricted folder.
then goto the restricted folder and try the search.
then post if it worked or not.
Dont worrry about starting a seperate topic, I'll ask TSG to move these posts into its own topic.