Originally posted by bal
TNSNAMES.ORA
***************
...
ORA817 =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = dsd)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = ora817)
)
)

...
try use here SID keyword instead of SERVICE_NAME. If it works, then there is an issue of backward compatibility flag on one of conf. assistant tab (sorry, I don't remember more exactly where it is). It comes with default installation.