Freepbx Admin login error

Dear All,
I have a working system with Asterisk 11.6.0 and Freepbx 2.11.0. Last week, when i tried to login in the freepbx, it says Username OR Password is wrong. And in the CLI i am getting the following message.

[2014-10-19 13:28:10] WARNING[1092]: security_events.c:566 add_ie: Required IE ‘50’ for security event type ‘12’ not present
[2014-10-19 13:28:10] NOTICE[1092]: manager.c:2623 authenticate: failed to authenticate as ‘admin’

I have crosschecked with the /etc/asterisk/manager.conf for the login credentials and everything is fine. But still i am not able to login.
enabled = yes
port = 5038
bindaddr =
displayconnects=no ;only effects 1.6+

secret =Password
read = system,call,log,verbose,command,agent,user,config,command,dtmf,reporting,cdr,dialplan,originate
write = system,call,log,verbose,command,agent,user,config,command,dtmf,reporting,cdr,dialplan,originate
writetimeout = 5000

Anybody faced same like issue ??

Thanks in Advance

Is your pbx on public or private network?

Its on Public network.