Feb 14, 2014 05:12 AM|Happy Chen - MSFT|LINK
Login failed for user ''. Reason: An attempt to login using SQL authentication failed. Server is configured for Windows authentication only. [CLIENT: 127.0.0.1]
According to your description, i would suggest you check out your connectionstring and make sure that it is ok.
if you use sa login, then you try Run following script in SQL Analyzer to change the authentication:
LOGIN sa ENABLE GO ALTER LOGIN sa WITH PASSWORD = '<password>' GO
please check out the link below for details:
SQL Server Asp.Net - “Login failed”
Hope it helps you.