client can`t acess database

i have 15 system windows 2000 server base domain network including dhcp on same dc one of the machine has oracle 9i database and my client application power builder 6.5 now freaquently i have problem of database connectivity some how if i remove ip add settings then it connects again but when i restart machine same thing repeat i got end of file communication channel, oracle not exist ,memory relam error (when i connect through sql)and when i try to connect through local admin account it works but in domain it fails to open even plz tell me what to do