I did some research and found that one of the possible causes would be that if the oracle account is locked, this error would appear, but the oracle account is not locked, as you can se below:
! bad user (oracle) Mon Apr 15 10:30:00 2013
What can be the problem?
cat /etc/shadow oracle:v.NiHxwn3VpQM:15800::::::
Edited by: Fabricio_Jorge on 15/04/2013 08:14
# cron service (explicit because of non-usage of pam_roles.so.1) cron account required pam_unix_account.so.1