HttpContext.Current.Identity Expiries

Hi
 
I am using HttpContext.Current.Identity to check that a user isAuthenticated and allow him acess to specific methods.
Once logged in the Context is set correctly and everything works as it should. After a while say a few minutes the value of the  HttpContext.Current.Identity.Name simply goes empty. Strangely enough this does not happen when testing the site locally it ONLY happens when the website has been published to the live enviroment {hosting space @ M6.net}
Any suggestion are greatly appreciated.
 
Thanks
 
Regards
Gabriel
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