Forms authentication

[verde4]

I want to ask you all about Forms authentication.
There is something happen that confusing me

I already set the authentication in web.config :

<authentication mode=&quot;Forms&quot;>
<forms name=&quot;.ASPXAUTH&quot; loginUrl=&quot;Login.aspx&quot; />
</authentication>

and login page :

FormsAuthentication.RedirectFromLoginPage(txt_UserID.Text, False)

The problem is..
If I use localhost (

http://localhost...)

, my application run well.
but if i use my computer name, my application always return to login page.
there is something I should do?

thanks for ur help
Angela