suddenly can't logon a kerberorised remote host.

[sam]

Dear all,

I don't know why I suddently can't logon to a remote host any more. I m 
using Heimdal Kerberos 5. I 've been using kerberos authenticatoin logon 
for a week or so. May be the ticket had been expired? How can I verify 
the tickets are expiered? What commands I should use?

Thanks
sam