Thanks for you reply. Today after shutting everything down for the weekend, the computers now see each other. The only change I made before this happened is one of the machines was 10.4.0 and all the others had the updates to 10.4.11. I upgraded this one machine from 10.4 to 10.4.11. then the next day nobody could connect to any other computer.
This is a wired network, with one laptop usually wired, but the Netgear router allows for wireless. Neither wired or wireless would connect to any other computer. The "alias" of all the computers would show up in some network folders but when you clicked on them the computer would unsuccessfully look for them until it timed out.
One technical guy I called says this may be a "hard lock out" and shutting the entire network down including routers might solve the problem. We may have done just that since we shut everything down over the weekend.
I'll post again if it happens again.
Thanks,