Different Browsers: Safari, Firefox, and Flock. Doesn't seem to make a difference.
Logging in as a different user: Didn't help.
Clearing the DNS cache using the terminal: Seemed to work at first, but doesn't really.
Replacing the default Comcast DNS with OpenDNS in my Belkin router: No effect
Disabling various parts of Norton Security Suite: same as above.
Clearing cached pages, history, and cookies doesn't seem to help much either.
The network utility returns the address 18.104.22.168 for wunderground.com, which is correct, and will return the correct web site if entered in the address bar of the browser. Putting in the name wunderground.com returns the web site for the washington post (which is 22.214.171.124).
The problem nearly always occurs when I try to access wunderground.com, though it happened only once with another web site I frequently access.
The computer is a Mac G4 with OSX 10.5.8 (Leopard), installed over Panther a few months ago. Recently (within the last month), I installed the Norton Security Suite (a freebee from Comcast), which has made it a prime suspect. I'm not quite ready to uninstall Norton and do a clean install of the system, but I'm considering that if I can't fix the problem with a less drastic measure.
I'm an experienced user and have done a lot of searching of the net to see if anyone else has experienced a similar issue, and there's nothing out there quite like this.
Edit: After I just posted this, the problem went away on its own, without any intervention, but I'm pretty sure it will be back.
Edited by GB Colburn, 03 April 2010 - 11:01 PM.