Network iBook to iMac booted with ext. HD in 10.4.3 not work

Question

I recently installed OSX 10.4.3 onto an external HD (LaCie) connected by Firewire to my old iMac, (I will henceforth call it "old iMac") that has only a 10GB HD. I kept the old OSX10.3.9 on the internal HD of the old iMac.
I can network thru a Lychsys router from either my iBook G4 or my other iMac to the old iMac as long as the old iMac is booted using the OSX10.3.9, but I cannot connect to it from those machines when the old iMac is booted thru the external HD in OSX10.4.3
From the old iMac I am able to network to the 2 other computers, ie their files can be seen from the old iMac, whether it is booted in OSX10.3.9 from the internal HD or inOSX10.4.3 in the external HD
I checked IP settings, and they are same in both OS's, also ran diagnostics undr TCP/IP. No help.
The problem appears to be associated with the OSX10.4.3 installed on the external HD.
Any ideas?
iBook G4, iMacDV   Mac OS X (10.4.3)  

Answer 1

Thanks for your reply.
1) I tried renaming /private/etc/smb.conf to smb-OLD.conf and restarting. I still couldn't hit the server, and when I ran testparm after that, it said that it couldn't find smb.conf. So it didn't create a new smb.conf file. (Please excuse me; I'm not very technical and I barely understood your reply!)
2) I also tried turning windows sharing off and back on; still can't hit the server.
3) I removed SMB in Directory Access, rebooted and re-enabled it, but I don't have any workgroup or wins settings to fill in. When I boot from my 10.4.0 drive (which IS able to log on to the server), workgroup is set to Workgroup, and wins is blank.
When I run testparm booted from my 10.4.0 drive, the settings are exactly the same as what I see booted from my 10.4.5 drive.
This is driving me crazy. Thanks again for your help, and again, any advice is welcome.