Sysadmin login working ( intermittently ) after R12 upgradation. All other logins working fine.

Facing a strange issue from last 4-5 months. Sysadmin login working ( intermittently ) after R12 upgradation i.e. taking time and mot the time error out with "Internal Server Error",whereas all other logins are working fine.
Error in error..log

 1356089596:151.110.228.159:2606:0:5,0] mod_oc4j: request to OC4J <hostname>:21860 failed: recv failed (errno=4)


egebc2d > select count(*) from  ICX_SESSIONS;

  COUNT(*)
----------
      1289

1 row selected.

egebc2d > select count(*) from FND_LOGINS;

  COUNT(*)
----------
    130848