Networks DNS problems? 1 user can connect, 2 can't!

I've been plagued with the family technical support dilemma - where I'm supposed to know everything, purely because I work in IT, but hey.

I've been through everything I can think of, but here's the scenario:

There's 2 PCs - one a wireless laptop, that connects to the internet fine, via a Linksys Wireless Router. The second is a desktop running XP. On the desktop, one user can connect to the internet (via a wired connection) fine. The other 2 users cannot - and this has only started within the past fortnight apparently.

I thought the router itself might be restricting access to the other 2 users, so it was reset, but still the problem occurs. I've run the network setup wizard on both non-functioning accounts, but no luck.

I think I've narrowed it down to DNS problems - as pinging 192.168.1.1 (router) works fine, suggesting it can see the router. Pinging google.com doesn't work - BUT pinging google's ip address (64.233.187.99 atm) does work. Which to me suggests that the user accounts can't communicate with domain names, but can communicate with the ip addresses themselves.

Internet Explorer itself proves useless though, as it wont connect to any ip or domain, including the router itself.

Any ideas? What can I do to get the 2 user accounts onto the internet again?

EDIT: All network settings appear to be identical - Windows Firewall has no affect either enabled or disabled.

 

would the one user on the desktop be the Administrator account and then two other users who cant surf the internet be limited users. Somthing could have changed that has edited the security policys of the other two users as to prevent windows from allowing access.

 

Good point, I'll ascertain if any are/aren't administrators.

As a last resort, I thought I could create 2 new accounts and migrate everything over from the old ones - as long as the new accounts worked online.