Central Administration shows error 26 - A network-related or instance-specific error occurred while establishing a connection to SQL Server

While Config FBA , BUT after CA web.config changes , My Central Administration shows an Error :

 A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 – Error Locating Server/Instance Specified)

Correlation ID: 89651359-9c57-4241-8254-eb3be052c4f0

Central Administration shows error 26 - A network-related or instance-specific error occurred while establishing a connection to SQL Server
Solution :

1- Open SharePoint Central Administration v4 Web.config File in VS2010 or notepad

2- Find this Node :

    <roleManager enabled="true">
      <providers>
      </providers>
    </roleManager>

(Under System.Web Node)

& Change Enabled to  false

& Now My CA works Well   :-)