Why does magento always come out of session

I increased my session timing to 1 hour in admin panel, but still most of items it throws me a开发者_StackOverflow中文版way (both in admin side/client side) from the authorised pages and redirects me to login page. What is the problem that am facing? I am using Enterprise edtion 1.9 and is there anything should i specify in the admin side.

Note:

Session storage is using file and i could see no prob with that directory in my server

Check the date, time, and time zone on the server. Make sure the time zone on your client computer is correct.

It is easy to encounter such problems when the time "looks right" but is actually applied against the wrong time zone, resulting in bad offset conversions ... aka "that session cookie I just set is already expired".

Check your php settings for gc.session-maxlifetime. That usually needs to be increased also.