Getting error while creating a new web app saying "The password supplied with the username domainname\username was not correct. Verify that it was entered correctly and try again"

Hi ,

I am trying to create a new web app using Central Administration in Sharepoint 2010 and getting an error "The password supplied with the username  was not correct. Verify that it was entered correctly and try again".

I tried running this command also "stsadm -o updatefarmcredentials -userlogin <domain\username> -password <newpassword>" but when it got executed it showed me "Access Denied".

What should i do ??

Thanks in advance.

Regards, Anurag