HttpContext.Current.User.Identity.Name blank

Hi,

 

 I am facing a weird  issue in my web application in which I am using asp.net membership with  forms authentication. The login is behaving irregular. Some times User is login but some times it is not. Then I checked actually the user name using  httpContext.Current.User.Identity.Name is blank.

After refresh the page many time then it works again for one time. I can not figure out whatz happning.

Kindly help.

 

Thanks.