Page title and permalink

Hi,

for a customer i must develop a website but only under WP 3.4.2.
i have a strange behavior, but maybe it is due to my limited knowledge of WP.

I created a page called “special areas” and i changed the permalink to “https://mycomputer/services” instead of “https://mycomputer/special-areas”.
Based on that page i created a menu item called “special areas”.

Since this permalink change, every time i click on the menu item “speacial area” it returns me to home page.

Why ?
i was thinking that changing the permalink value was ok.
where is my mistake and what should i do to make it work as i want ?
thx