samba broken

[Linda]

This week my samba connection between my XP computer and my 
Ubuntu 10.04.3 computer has quit working.  When I checked 
the /etc/samba file had lost smbpasswd so I copied contents 
of /etc/samba from my backup onto the Ubuntu computer but it 
still does not work. I can ping from ubuntu to XP and vice 
versa. I also bring up the XP computer under places network 
as read only file systems. However the XP computer will not 
even acknowledge the Ubuntu computer exits using Network 
Places on XP or using Search for the computer. I checked 
Hosts and lmhosts on XP and they are still there.  Any ideas 
on why this has suddenly ceased working
I'm leaning towards removing samba and going through a fresh 
setup since I'm stuck but thought someone might have a 
suggestion on what happened
                                  Thanks
                                    Linda