I was browsing for a solution for the error thrown by the MOSS when you are using a webpart which uses connection to database... "Request for the permission of type 'System.Data.SqlClient.SqlClientPermission, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed." a possible solution is like this : 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: * 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 :\Program Files\Common Files\Microsoft Shared\Server Extensions\60\Config) * Add the following element to the SecurityClasses section of this config file: * In the PermissionSet section of this configuration file, add the following: If you still run into the error, try adding these settings to the wss_mediumtrus...