don't use a wildcard in the enable/disable statement..use the actual name of the group, and don't forget the # symbol

Additionally, don't have groups with the same name, or mIRC won't know which one to enable/disable, so it defaults to doing them all

Names are, technically, limited in size and characters...if you go too big or use a character that's not acceptable, you'll get a message in your status window saying Invalid Group Name
P.S.: The maximum size is 1024 characters (so there's lots of room)