我已经看到了其在machine.config文件附加，自终止节点的人报告。删除它解决了他们的问题。 machine.config中发现的 \的Windows \ Microsoft.net \框架\ vXXXX \配置。如何根据该框架的许多版本安装，包括32位和64位变种你可以有多种配置文件。

I have seen reports of people having and additional, self terminating node in the machine.config file. Removing it resolved their issue. machine.config is found in \Windows\Microsoft.net\Framework\vXXXX\Config. You could have a multitude of config files based on how many versions of the framework are installed, including 32 and 64 bit variants.

<system.data>
    <DbProviderFactories>
        <add name="Odbc Data Provider" invariant="System.Data.Odbc" ... />
        <add name="OleDb Data Provider" invariant="System.Data.OleDb" ... />
        <add name="OracleClient Data Provider" invariant="System.Data ... />
        <add name="SqlClient Data Provider" invariant="System.Data ... />
        <add name="IBM DB2 for i .NET Provider" invariant="IBM.Data ... />
        <add name="Microsoft SQL Server Compact Data Provider" ... />     
    </DbProviderFactories>

    <DbProviderFactories/>  //remove this one!
</system.data>