Thank you for your post, and I apologize for the late reply.
I am looking at the case notes from Technical Support, and it looks like you finally got this resolved in December. I can post the case notes from the Technician's notes, but it would be more beneficial to other forum users if you post in your own words. This may help others who encounter the same problem.
Sorry for the late response, but I just remembered I had posted this a long time ago. But it was this in a nutshell. FMS10 did not like me using en0 (ethernet port#1) on the Master machine. After switching it to en1 and a private manually configured IP like 192.168.1.100 - the master could communicate with the slave on the second machine. I also added 192.168.1.101 as the router IP, the IP of the slave machine. Maybe it is just my equipment running 10.5.6 Leopard. But after testing the speed of the master slave combo, I was disappointed in the performance since FMS10 ran much faster on a single machine. Doesn't seem right, but I was able to utilize a robust, fat database to time queries and snappiness in the response. The master/slave 2 machine configuration is slower. So I reluctantly reconfigured back to a single machine and using a second machine with APache and Lasso to distribute data via the web from the FMS10 machine.