I did not want an excel file's users to insert new rows or columns (etc) and
hence i locked all those cells.

I then went and protected the sheet
1. Enabled "Protect worksheet and contents of locked cells' checkbox
2. specified a password
3. checked only the items i wanted the Users to perform
4. So, i said "Allow all Users of this worksheet to:"
4.1 Select locked cells
4.2 Select unlocked cells
4.3 Format cells
4.4 Format rows
4.5 Sort
4.6 Use AutoFilter
4.7 Edit Objects

I can now right click on any row and the "Insert' and "Delete" options are
disabled - which is correct.
The "Hide" and "Unhide" options are enabled - which is correct.

Now, after some time or after the file is closed and opened, the "Hide" and
"Unhide" options are disabled.

Why are these settings being lost?

It makes me mad, as i have sent this file to 10 users and the settings are
retained for a while and go away after sometime....

Thanks for the help..