JDE hung for KNT0000306, SEC0000002

My issue is all users cannot logon JDE suddenly at work, a few minutes(like 10 to 15 min) later, the service back to normal automatically.

OS:AIX 5.0

DB:Oracle 9i R2

JDE version: 7.333

JDENET:

serviceNameListen = 6009

serviceNameConnect = 609

maxNetConnections = 800

maxNetProcesses = 10

maxKernelranges = 13

netTrace = 0

Fat client error = SEC0000007 and Enterprise Server error = SEC000002

I've checked jde logs on server  :

.......

1.KNT0000306 JDENET Error = eTimeOut     jdeksec.c3681

2.SEC0000002 - Unable to connec to security server JDEProd1    jdeksec.c929

This may or may not work depending on the databases' security 

3.JDB1100015 - Failed to complete Security check   jdb_ctl.c3042

4.Could not initialize the environment for the user, JDESCH in the environment PD7333  sc_lnch.c1515