What is the service name of your instance. In the tnsnames.ora file, you might want to consider specifying the service_name instead of the SID_NAME. Can you make a client connection to the server using sqlplus

Code:
       sqlplus username/[email protected]
Regarding the hostname recognetion. consult with your system adminstrator(s) about the DNS looks up configureation and etc.

How did you come to a conclusion that the sqlnet is slow?

To make the regular connection try

Code:
     SID_LIST_LISTENER= 
         (SID_LIST= 
             (SID_DESC= 
                (SID_NAME=NEWFLT) 
                (PROGRAM = ORACLE$DISK:[ORACLE8.ORACLE817.network.admin]orasrv_netv2_NEWFLT.com) 
                 (prespawn_max=20) 
                 (prespawn_list= 
                        (prespawn_desc= 
                             (protocol=tcp) 
                             (pool_size=15) 
                             (TIMEOUT = 5) 
                        ) 
                  )
              ) 
 
              (SID_DESC= 
                 (GLOBAL_DBNAME = ... )
                 (ORACLE_HOME = ...)
                 (SID_NAME=NEWFLT)  
               )  
          ) 


tnsname.ora

   RF1.WORLD = 
    (DESCRIPTION = 
        (ADDRESS_LIST = 
           (ADDRESS = (COMMUNITY = tcp.world)(PROTOCOL = TCP)(HOST = ... )(PORT = 1526)) 
         ) 
         (CONNECT_DATA = (SERVICE_NAME = NEWFLT)) 
     ) 



   RF2.WORLD = 
    (DESCRIPTION = 
        (ADDRESS_LIST = 
           (ADDRESS = (PROTOCOL = TCP)(HOST = ... )(PORT = 1526)) 
         ) 
         (CONNECT_DATA = (SERVICE_NAME = NEWFLT)) 
     )
Also Could you post the sqlnet.ora file also.