I have a DNN 5.2 installation which has to support various multi-language sites. I am experiencing two problems trying to enable and edit languages. 

Firstly, I can only enable any given language on 1 portal. If I try to enable a language on a second portal, I get the following error:

Error: is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: Cannot insert duplicate key row in object 'dbo.Languages' with unique index 'IX_Languages'. The statement has been terminated. ---> System.Data.SqlClient.SqlException: Cannot insert duplicate key row in object 'dbo.Languages' with unique index 'IX_Languages'. The statement has been terminated. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlDataReader.ConsumeMetaData() at System.Data.SqlClient.SqlDataReader.get_MetaData() at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) at System.Data.SqlClient.SqlCommand.ExecuteScalar() at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteScalar(SqlConnection connection, CommandType commandType, String commandText, SqlParameter[] commandParameters) at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteScalar(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters) at Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteScalar(String connectionString, String spName, Object[] parameterValues) at DotNetNuke.Data.SqlDataProvider.AddLanguage(String cultureCode, String cultureName, String fallbackCulture, Int32 CreatedByUserID) at DotNetNuke.Services.Localization.Localization.SaveLanguage(Locale locale) at DotNetNuke.Modules.Admin.Languages.EditLanguage.cmdUpdate_Click(Object sender, EventArgs e) --- End of inner exception stack trace ---

Secondly, when trying edit resource files in the Language Editor, when trying to save the file I get the error:

A File Operation Failed. Please Check Resource File Permissions So Files Can Be Edited.

This, despite the fact that the Network Service account has full permissions to the DNN installation directory on the server.