OSX Jag DNS woes

[SeaSoft Systems]

This is driving me nuts.

My eMac (OS10.2.8) is periodically losing its DNS resolution 
capability. The symptoms:

- I begin getting nonsensical "Server not found" errors when browsing 
the net (in Safari or IE), typically out of the blue after a couple 
hours of successful surfing.

- Usually (probably always) mail goes down at the same time with an 
"unable to receive mail", "mail server mail.west.net can not be 
contacted on port 110" error.

- An OS 8.6 box on the same LAN behaves normally (mail and http) 
whilst the eMac remains internet-deaf and dumb, so my ISP DNS 
resolution is fine.

- When this happens, I *can* connect to external sites via their IP 
numbers, but not with their URLs.

- I can log into the eMac (via telnet) and file share with it (using 
AFP) while it is  misbehaving.

- A check of my network settings shows no abnormalities (i.e., the 
ISP DNS addresses are right where they belong; they haven't 
disappeared or anything).

- Console sometimes shows nothing whatsoever abnormal, but at least 
one time showed a lot of java error-type stuff.

Things I have tried:

- Permissions repair does not fix the problem.

- Logging out and back in under the same user does not fix the problem.

- Logging out and back in on a pristine admin account does not fix the problem.

- *Rebooting* the eMac completely restores functionality.

This is obviously some sort of DNS daemon failure, but I am pretty 
severely DNS-knowledge impaired. Perhaps OSX is losing it's grip on 
my ISP's DNS addresses, but they appear ok in the network settings 
pane whilst this is happening.

Has anyone seen anything like this? A JAG issue perhaps? Ideas for 
fixing it? Rebooting a couple times a day to eliminate this problem 
is not why I moved to OSX... :(



Regards,

Richard