Look at your /etc/services. What is defined at port 139/tcp? If nothing is defined, then add a line like this:

netbios-ssn     139/tcp

Similarly for 137/udp, you should have an entry like:

netbios-ns	137/udp

Next, edit your /etc/inetd.conf and add two lines like this:

netbios-ssn stream tcp nowait root /usr/local/samba/sbin/smbd smbd 
netbios-ns dgram udp wait root /usr/local/samba/sbin/nmbd nmbd 

The exact syntax of /etc/inetd.conf varies between UNIXes. Look at the other entries in inetd.conf for a guide.

Some distributions use xinetd instead of inetd. Consult the xinetd manual for configuration information.