[Samba] why does samba work one way

[Mat]

i can mount any PC share but i can not get any networked pc to see my linux 
box

ages ago i had an iMac running yellow dog linux, set samba up and was able to 
mount pc shares and when i opened network neighbourhood on pc it had my linux 
icon there and this would open too so i could share files both ways

now running red hat and i can not get the pc's to open my linux box, the icon 
is there but i get ......path unobtainable...

i have done a tcpdump and the pc sends about 4 packets before it is refused

all i can assume is there is something wrong with smb.conf, although this is a 
carbon copy of the one i used before


any ideas, this has now taken a month help!!

cheers m