You have selected 1 post that is not part of this thread. Quote this post as well, or deselect this post.
That message is displayed if you have clicked the multi-quote button on a post, but then have browsed to another thread and clicked reply.
Ah! Thanks for explaining the message.
Any clarification on the different between the need for do=newreply&noquote=1&p=$FIRSTPOSTID, $FIRSTPOSTID and if $post[postid] is even needed?