Decrypting Kerberos tickets

I'm doing a network capture using wireshark targeting some Kerberos traffic (ticket cache is flushed, then a request is made to a file server - thus generating the AS-REQ/AS-REP/TGS-REQ/TGS-REP sequences) and I'd like to see the encrypted parts of the tickets (eg timestamps used as authenticators). I've found http://i1.blogs.msdn.com/b/spatdsg/archive/2009/03/26/more-kerberos-fun-with-pac-s.aspx which is pretty straightforward. However, by doing the steps presented there, the encrypted part is never decrypted. Wireshark works just fine, because with its own samples, decoding works great (http://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=view&target=krb-816.zip). So obviously there must be something wrong in the process. The client I'm using is a Windows 7, against a 2008 R2 DC. I tried exporting the keytab under different encryption formats (both RC4-HMAC-NT and AES256-SHA1) using my own principal name using ktpass, but neither worked. Could you help me figure out what's wrong ?