I have two macs, running Leopard 10.5.8. One is the 13" MBP connected via WiFi, and the other is a 24" 2008 iMac, connected via ethernet.

There are at least another 6-10 machines (windows and mac) awake on the network (with shares) at any given time, yet there are plenty of times where I cannot see any devices/shares in either my "Shared" section in Finder, nor can I see any computers in "Network" in Finder.

Restarting doesn't help. I've restarted all the networking gear in the house to no avail.

Our network is a series of gigabit switches connected to a D-Link gaming router. I believe we use OpenDNS, and our provider is Cox.

I hate having to use "Go -> Connect to Server" to browse to commonly used file shares (by IP). I'd like to know why my shares do not always and consistently appear in Leopard.

Edit: I ran OnyX this morning, and performed the cleaning and maintenance operations (including disk permissions) on both my Macs, and at least one of my macs has started showing network devices again. (the other is still going). No idea how long this will last.

Any ideas as to what is causing this issue, and how to prevent it?

Edit 2: Aaaand there the shares go again. So running OnyX is not a permanent or reliable fix for this issue.

Edit 3: After a clean reinstall and update, network shares are still unreliable. The SMBClient command mentioned in comments shows me the information it's supposed to show, but the shares do not appear in the shared section. They'll also vanish at random and reappear at random throughout the day.