>I am trying to connect to a Oracle 9i via MS odbc driver (mdac 2.6) from a
Works fine here with the same configuration. Do you have multiple 9i homes?
You might take a look at the registry keys:

For 8i
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSDTC\MTxOCI]
"OracleXaLib"="oraclient8.dll"
"OracleSqlLib"="orasql8.dll"
"OracleOciLib"="oci.dll"

For 9i mine says

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSDTC\MTxOCI]
"OracleXaLib"="xa80.dll"
"OracleSqlLib"="SQLLib80.dll"
"OracleOciLib"="oci.dll"