Help with SDM

I am having a problem calling up my SDM over https .This is the error message i got

Secure Connection Failed
An error occurred during a connection to 192.168.0.1.

You have received an invalid certificate.  Please contact the server administrator or email correspondent and give them the following information:

Your certificate contains the same serial number as another certificate issued by the certificate authority.  Please get a new certificate containing a unique serial number.

(Error code: sec_error_reused_issuer_and_serial)

The page you are trying to view can not be shown because the authenticity of the received data could not be verified.

    * Please contact the web site owners to inform them of this problem

This is the setting i put on the router

Router(config)# ip http server
Router(config)# ip http secure-server
Router(config)# ip http authentication local
Router(confi)#username stanley privilege 15 password 0 ma7yGGas088RVb97162

sh run | begin line
line con 0
 password py##otuti$$router
 login
line aux 0
line vty 0 4
 password py##otuti$$router
 login
 transport input telnet ssh
line vty 5 193
 privilege level 15
 login local
 transport input telnet ssh
!
!
webvpn context Default_context
 ssl authenticate verify all
 !
 no inservice
!
end