ASP.NET: Cannot create a user instance for sql server

Problem: Form authentication is setup and user has been created but cannot login using form authentication.

     1. Have deleted aspnet.log file from solution explorer-app_data folder. then it does show new message.
Cannot open user default database. Login failed.
Login failed for user 'GARDEN\ASPNET'.

    2. So follow the step to in  http://www.blogger.com/blogger.g?blogID=3635402301628205031#overview/postNum=3