Master/Slave loading issues

[Chimento, Douglas]

All,
Scenario:
	Suppose Server A is master for foo.com 
	And Server B slave of A.
	Server B named.conf looks like this: 
##############################################
options {
        directory "/var/named";
        check-names slave ignore;	
  };

zone "foo.com" {
      type slave; masters { A; };
//        type master;
        file "foo.com";
};
##################################################


What I want to do is change B to be master or authoritative for foo.com

So now I have this  in named.conf 
#######################################
options {
        directory "/var/named";
        check-names master ignore;	
  };
zone "foo.com" {
	  type master;
        file "foo.com";
};
######################################

However in my logs , foo.com gets rejected because of this:
bar.foo.com: CNAME and OTHER data error

I understand the error and I know what is means.
My Question to you is "Why does the slave setting load  the zone but the
master setting rejects foo.com"?

FYI:
1) I have no control over server A , I don't know what version of DNS it's
running 
2) I run this command "dig +short @A  bar.foo.com" and get this back from
server A : Bar.foo.com IN A 1.2.3.4 Bar.foo.com IN CNAME  nothing.foo.com
3) the command:  dig +short @A  -t cname bar.foo.com  ...  returns nothing 
4) server B is running bind 8.3.3