java.security.PrivilegedActionException on Configuring SSO using SPNEGO Tomcat 7

Question

I am trying to get SSO working using SPNEGO for Tomcat 7 with IBM JDK. We are using "org.apache.catalina.authenticator.SpnegoAuthenticator" for authentication which calls com.sun.security.jgss.krb5.accept. The configuration for it is

com.sun.security.jgss.krb5.accept {
    com.ibm.security.auth.module.Krb5LoginModule required
    principal="[email protected]"
    useKeyTab=C:/Downloads/tomcat/conf/xxx.keytab
    credsType=acceptor
    debug=true;
   };

I tried with Java 6 (SR9), 7 (SR1,SR5), but I always get stuck on below error.

java.security.PrivilegedActionException: org.ietf.jgss.GSSException, major code: 11, minor code: 0
    major string: General failure, unspecified at GSSAPI level
    minor string: Desired initLifetime zero or less

Can anybody point to anything that I have missed?

-Thanks