DRCP erroring in 11g

Im trtying to get DRCP to work with 11g. the error im getting is ;

"ORA-12523: TNS:listener could not find instance appropriate for the client
connection"

The tnsnames.ora entry is;
--------------------------------
o11gtest =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = server)(PORT = 1599))
)
(CONNECT_DATA =
(SERVICE_NAME = o11gtest)
(SERVER = POOLED )
)
)

If I take the "(SERVER = POOLED " section out then I can connect as you would expect.

The connection pool is started ;

1* select POOL_NAME,NUM_OPEN_SERVERS from v$cpool_stats
SQL> /

POOL_NAME NUM_OPEN_SERVERS
------------------------------ ----------------
SYS_DEFAULT_CONNECTION_POOL 4

SQL> select status from dba_cpool_info
2 /

STATUS
----------------
ACTIVE

services in the listener;
----------------------------
Services Summary...
Service "o11gtest" has 1 instance(s).
Instance "o11gtest", status UNKNOWN, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0
LOCAL SERVER

Any ideas? Its starting to drive me nuts...