NY has complex rules on procedure and service. From what you explain in your question you had been in NY before you were served, the fact that you weren't there when you were served does not mean that the court lacks jurisdiction. Jurisdiction over you comes from your significant ties to the state and since the court action is probably based on something that happened while you were in NY they have jurisdiction over you.
As for service, NY prefers personal service. However, if a few attempts at personal service are unsuccessful then the rules allow for you to be served by mail and other ways depending on the circumstances. Chances are your service argument will not be successful unless you can show that the server did not follow procedure.
Another note. If NY can't get jurisdiction over you "in personam jurisdiction" then they will attempt to get jurisdiction over your NY property "in rem jurisdiction." If you wish to protect your NY house you should hire a NY attorney.
Edited by Law Answer Man on July 23 2008 at 4:24 PM
Please be aware that this response is legal education, not legal advice. No attorney-client relationship is created by this answer. I really appreciate Feedback!