Since upgrading to 10.5.7, network "fades" out

Question

My trusty old G5 still works great for the tasks I require of it and has faithfully responded to every system upgrade until 10.5.7. When I first boot it up, my account is set to launch Camino (my "second" browser) with a special URL that tracks stats on one of my websites in real time, then the system launches Microsoft Word 2008 and SuperDuper. If I don't do anything right away SuperDuper will do an automatic backup of my data drive.
During the first five or ten minutes after startup or log in, I can see my local network, the Internet and print to my printer without any problems. After a short period, I can no longer print or see my local network, though I CAN reach the Internet without any problem.
The G5 uses wired ethernet to a Verizon Westell DSL modem (an older model, one of the worst, but it usually works fine for me). I also have other wired and wireless Macs and PCs on the local network. None of them, including both newer and older Macs with 10.5.7, have this problem.
I can log out and log back in and the local network works again for a short period. I have disabled the apps that launch at startup and they do not appear to be causing the problem.
Why do I lose only the local network and not the Internet?
Any suggestions how I can determine what else may be causing this erratic behavior?

Answer 1

@ satcomer & shivsetlur
Thanks for the tip on Console - though I've been aware of it for years I've never actually used it for troubleshooting.
As sometimes happens in life, when you focus on a problem suddenly the problem goes away of its own accord without any obvious action. Yesterday the local network problem continued, as it has for months since the 10.5.7 upgrade. This morning, after reading your two posts, which arrived as emails, I immediately tried my network. The computer had started up on its own as it does every morning, and after I sat down in front of it two hours after that boot, the local network worked normally. Usually I would have to reboot to see the local network, or if I saw the local network in my Sidebar, clicking on any device there would result in the name disappearing or nothing happening at all.
This morning everything worked and now, several hours later, still works.
It's a l m o s t as frustrating as the original problem. I haven't added or changed anything since my original post here.
I will update this post should the problem re-occur or, after a week or two, everything is still working.
In the meantime I will try to stop scratching my head in order to prevent injury.