C# - Object Reference Error Even When Object Is Not Null?

i have an application wherein i have incorporate a "Remember Me" feature for the login screen. I do this by creating a cookie when the user logs in for the first time, so next time when the user visits the site i get the cookie and load the user information.

i have written the code for loading user information in a common class in the App_Code folder...and all my pages inherit from this class.

code for loading the user info is as follows:

public static void LoadUserDetails(string emailId)
{
UsersEnt currentUser = UsersBL.LoadUserInfo(emailId);
if (currentUser != null)
HttpContext.Current.Session["CurrentUser"] = currentUser;
}

Now the problem is i get an "Object reference" error when i try to store the currentUser object in the session variable (even though the currentUser object is not null). However the password property in the currentUser object is null.