Problema com webservice

Salve

Eu tocom o seguinte problema, eu tenho um webservice com o seguinte codigo

string str_conn = "User ID=sa;Initial Catalog=f203410;Data Source=.";public DataSet realiza_conexao(string sql){	SqlConnection _conn = new SqlConnection(str_conn);	SqlCommand _command = new SqlCommand(sql,_conn);                SqlDataAdapter dtaConexao = new SqlDataAdapter(_command);	DataSet ds = new DataSet();	dtaConexao.Fill(ds);	this.flag_real_con_ok=true;	return(ds);}

onde eu quero pasar uma string "select * from tabela" e ele me retorna um tadaset com tudo que ele encontrar mas acontece que ta dando o seguinte erro

System.Data.SqlClient.SqlException: Login failed for user 'sa'.   at System.Data.SqlClient.ConnectionPool.GetConnection(Boolean& isInTransaction)   at System.Data.SqlClient.SqlConnectionPoolManager.GetPooledConnection(SqlConnectionString options, Boolean& isInTransaction)   at System.Data.SqlClient.SqlConnection.Open()   at System.Data.Common.DbDataAdapter.QuietOpen(IDbConnection connection, ConnectionState& originalState)   at System.Data.Common.DbDataAdapter.FillFromCommand(Object data, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)   at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)   at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet)   at csbank_ns.csbank.realiza_conexao(String sql) in d:\sites\csbank_ws\ws_csbank.asmx.cs:line 163   at csbank_ns.csbank.realiza_investimento(String sql) in d:\sites\csbank_ws\ws_csbank.asmx.cs:line 85

onde eu errei, será que é na string, pois nela não tem a senha do sql server

oq eu faço??