See answer in microsoft.public.excel.

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In article .com,
wrote:

Hi everyone,

This is my problem i have this file which has a lot of info on it and
obviously certain clients shouldn't see all the info in particular
columns thus i have protected the spreadsheet and the workbook so that
nobody can make changes to it, however i noticed recently that if I
manually copy all of the content from existing spreadsheet and export
it into a new spreadsheet voila! boom all my hidden info comes up here,
keep in mind the option for unhide is greyed out too on the protected
document.

could someone tell me whether this is a software glitch or is there
anything else perhaps i missed out on?

Any help on this would be greatly appreciated!