FULL PRODUCT VERSION :
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
Server account has constrained delegation.
After SpNego is established with the client, GSSContext.getDelegCred() returns a GSSCredential that is wrapping a Krb5ProxyCredential
Then, trying to that GSSCredential to create another GSSContext, and call GSSContext.initSecContext. Receives the following exception:
...
Caused by: GSSException: No valid credentials provided (Mechanism level: Failure unspecified at GSS-API level (Mechanism level: Generic error (description in e-text) (60) - Client principal does not match))
  at sun.security.jgss.spnego.SpNegoContext.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at com.mellmo.roambi.http.auth.spnego.SPNEGOAuthScheme.authenticate(SPNEGOAuthScheme.java:368)
  ... 404 more
Caused by: GSSException: Failure unspecified at GSS-API level (Mechanism level: Generic error (description in e-text) (60) - Client principal does not match)
  at sun.security.jgss.krb5.Krb5Context.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at sun.security.jgss.spnego.SpNegoContext.GSS_initSecContext(Unknown Source)
  ... 408 more
Caused by: KrbException: Generic error (description in e-text) (60) - Client principal does not match
  at sun.security.krb5.KrbCred.<init>(Unknown Source)
  at sun.security.jgss.krb5.InitialToken$OverloadedChecksum.<init>(Unknown Source)
  at sun.security.jgss.krb5.InitSecContextToken.<init>(Unknown Source)
  ... 412 more

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Server account has constrained delegation.
After SpNego is established with the client, GSSContext.getDelegCred() returns a GSSCredential that is wrapping a Krb5ProxyCredential
Then, trying to that GSSCredential to create another GSSContext, and call GSSContext.initSecContext.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
expected GSSContext.initSecContext to be successful.
ACTUAL -
saw an exception
...
Caused by: GSSException: No valid credentials provided (Mechanism level: Failure unspecified at GSS-API level (Mechanism level: Generic error (description in e-text) (60) - Client principal does not match))
  at sun.security.jgss.spnego.SpNegoContext.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at com.mellmo.roambi.http.auth.spnego.SPNEGOAuthScheme.authenticate(SPNEGOAuthScheme.java:368)
  ... 404 more
Caused by: GSSException: Failure unspecified at GSS-API level (Mechanism level: Generic error (description in e-text) (60) - Client principal does not match)
  at sun.security.jgss.krb5.Krb5Context.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at sun.security.jgss.GSSContextImpl.initSecContext(Unknown Source)
  at sun.security.jgss.spnego.SpNegoContext.GSS_initSecContext(Unknown Source)
  ... 408 more
Caused by: KrbException: Generic error (description in e-text) (60) - Client principal does not match
  at sun.security.krb5.KrbCred.<init>(Unknown Source)
  at sun.security.jgss.krb5.InitialToken$OverloadedChecksum.<init>(Unknown Source)
  at sun.security.jgss.krb5.InitSecContextToken.<init>(Unknown Source)
  ... 412 more

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
I patched KrbCred.java but removing the following check:
 /*
        if (!serviceTicket.getClient().equals(client))
            throw new KrbException(Krb5.KRB_ERR_GENERIC,
                                "Client principal does not match");
        */

and I was able to proceed.