Help me on login Authentication on localhost

Hi,
This is the Exact Error Message im getting whenever i log in from a locahost. It gives no problem whenever i debug the application. But as soon as i create a virtual directory and access using localhost and the app name it gives me this error or it wount login at all without any error also.

"Cannot open user default database. Login failed.
Login failed for user 'WORKSTATION1\ASPNET'. "

Hope someone can help me with this.
Thanks in advance
Regards
Hamar