Things to keep in mind:
In MiamiDX (don't know if this applies to AmiTCP), hostnames need to be manually matched up to IP addresses. If the addresses change (DHCP), the settings must be adjusted.
Samba needs the nmbd and smbd daemons running to work properly (smbd isn't really mentioned in the AmigaSamba config guide). The nmbd allows the PC to actually access the Amiga, smbd will bring the Amiga up in the Network Neighborhood listing. I'm sure they do other things, too, but I don't know what.
For some reason, the nmbd no longer works on my home network (though it did work at college - probably a PC problem). The nmbd is failing to resolve something, and not starting. The samba logs can help here. The Amiga can read the PC, but not vice versa.
It sounds like we might have the same problem. Check your nmbd logs to see what they say.