WRT54G can ping internet, but connected devices cannot.

Question

When I do a factory reset of our WRT54G router and configure it for our setup, everything works fine for a while (undetermined, random amount of time). We use it primarily for wireless access, and connect an iphone, ipad, mac, pc devices to it with no problem and can access the internet fine.
After some period of time, all devices can still connect to the WRT54G via wireless, but cannot access the internet either by browser or ping/tracert commands. Meanwhile, the WRT54G diagnostics can successfully perform pings and tracerts to both IP address and URLs (so DNS *is* working fine)
I connected a computer to the WRT54G via cat5 cable while the wireless devices could not access the internet, and the wired computer could *not* access the internet either. However, from the admin section of the WRT54G we could ping/tracert with no problems.
Any ideas what causes this to drop and what we can do (other than factory reset) to fix it, and perhaps to prevent it?
..Rick..

Answer 1

This isn't a home setup.  My wrt54G is connected to a DMZ switch which is connected to our gateway router and then out to the 100mpbs pipe.
All of our LAN is working fine, and as I mentioned in the original post, the WRT54G can always ping an external site (both via URL and IP address), as well as being able to do a traceroute.
When the connected devices can no longer get to the internet through the router, the router can still do the pings and traceroutes, so I conclude that there is no interruption in internet service. It stops at the WRT54G.  It always accepts wireless connections.