The bylaws of our HOA state that a quorum is 51% of the membership. The question is how is "membership" defined? I think it is anyone who is an owner of a condo in the association. Others think you have to be in good standing to be considered a member. I believe you are a member whether you are in good standing. So, a quorum is 51% of all owners (whether they've paid assessments or not). An owner attending a meeting would be counted to make a quorum even if he is not allowed to vote because he is not in good standing.

What does the bylaws say about defining what a member is ? If not they need to pass a rule defining what it is..

If the state statutes and the by-laws are silent on that question, if there is no provision explicitly stating that delinquent members are not allowed to vote, it seems to me that you have a very good argument that "a member is a member" and good standing is not required to vote.