Errors related to your .NET apps that use SQL clients:
Request for the permission of type
System.Data.SqlClient.SqlClientPermission,
System.Data, Version=1.0.5000.0, Culture=neutral,
ublicKeyToken=b77a5c561934e089 failed.
Reason: This is due to SharePoint Portal Server and Windows SharePoint Services implementation of .NET Code Access Security (CAS). A solution that addresses the aforementioned error is cited below.
Fix: Locate and open the wss_minimaltrust.config file (NOTE: If you've gone with the default SharePoint or WSS install, this file is located at <INSTALL_DRIVE>:\Program Files\Common Files\Microsoft Shared\Server Extensions\60\Config)
Add the following element to the SecurityClasses section of this config file:
<SecurityClass Name="SqlClientPermission"
Description="System.Data.SqlClient.SqlClientPermission, System.Data,
Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
/>
In the PermissionSet section of this configuration file, add the following:
<IPermission class="SqlClientPermission" version="1" Unrestricted="true" />
References:
http://blogs.msdn.com/lamonth/archive/2005/02/13/372075.aspx