Window Live Mail won’t sent to everyone listed in group contact

I have 8 people set up in a group contact folder and when I email that group it will randomly ignore a couple of the people.   I've tried deleting the group and re-creating it and it still leaves off a couple people.  However when I go in and view the contact group they are clearly in there.   I have no problems getting messages to them separately or manually adding the names to the recipient list.  Only have issues when I try to use the 'group' list.   Any suggestions on how to fix?