error on monitoring mssql db

i added SNMP service and sqlserveragent on window 2000 server
using mib browser i can get information on
mssqlSrvTable,mssqlSrvInfoTable,mssqlSrvConfigParamTable.mssqlSrvDeviceTable
but with the same method i cant i get information on
mssqlDbTable,mssqlDbInfoTable,mssqlDbOptionTable,msswlDbDeviceTable

this is the error message after trying to get information of mssqlDbInfoIndexSpace in mssqlDbInfoTable
Request failed or timed out. Response PDU received from 10.x.x.x
Error Indication in response:
A general failure occured
Errindex: 1
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

what am i done wrong ? Please help