ASP.NET C# SQL Connection problem

Jeg har et ASP.Net C# website. Sitet henter en række funktioner som henter oplysniger fra en MS SQL database (Version 9.00.4035.00). I hver metode som tilgår databasen opretter jeg et SqlConnection object som vist her:

SqlConnection conn = new SqlConnection(MSCRM_ConnectionHandler.GetSqlConnectionString());
SqlDataAdapter ad = null; ;
DataSet ds = null;

string sql = "SELECT * FROM........"

using (conn)
{
  SqlCommand cmd = new SqlCommand(sql, conn);
  ds = new DataSet();
  ad = new SqlDataAdapter(cmd);
  ad.Fill(ds);
}

Hver eneste metode virker fint hver for sig, MEN når de bliver kaldt på stribe for at hente alle oplysningerne ud så får jeg følgende fejl ved en af metoderne:

Error Code: -2146232060
Error Message:
A severe error occurred on the current command.  The results, if any, should be discarded.
A severe error occurred on the current command.  The results, if any, should be discarded.

StactTrace:
"  at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)\r\n  at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)\r\n  at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)\r\n  at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)\r\n  at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()\r\n  at System.Data.SqlClient.SqlDataReader.get_MetaData()\r\n  at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)\r\n  at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)\r\n  at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)\r\n  at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)\r\n  at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)\r\n  at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)\r\n  at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)\r\n  at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)\r\n  at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)\r\n  at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet)\r\n  at ApplicationFunctions.GetSupportQueueItems(List`1 supportqueuesid, String callinguser) in c:\\Minerva\\Website\\App_Code\\ApplicationFunctions.cs:line 793\r\n  at _Default.GetSupportQueueActivities() in c:\\Minerva\\Website\\Default.aspx.cs:line 229\r\n  at _Default.Page_Load(Object sender, EventArgs e) in c:\\Minerva\\Website\\Default.aspx.cs:line 54"


Hvis jeg bytter rundt på rækkefølgen af metoderne så kommer samme fejl bare ved en anden metode.
Har prøvet at google på Error Code men det gav ikke rigtig noget. Nogen forslag???