Would you use a certificate from your own company or from a national company, you may need to add it to the list of certificates that Mac OS X trusts — it ships with a list of known certificates that can be expanded.
You should find a link about how to do that in the talkbacks on this page. Note however that I have not tried it myself.
About your smart card issues, may I suggest that you post on the Apple Discussions ? You will find lots of experienced users who will be able to help you in greater detail that we could here.