Troubleshooting - Internal intranet not working on certain machines

Hi All,
We have Sage CRM which runs on microsoft IIS on an internal network, most machines can see the web pages fine apart from two.
The two machines are running win xp sp2 as are all the other machines on the network.
When trying to access the site, we recieve the following i.e. error:
The requested URL could not be retrieved
While trying to retrieve the url: http://servername/crm/eware.dll
the following error was encountered:
unable to determine IO address from hostname for "servername"
the dnsserver returned:
DNS Domain "Servername" is invalid: Host not found (authoratative)
This means that:
the cache was not able to resolve the hostname presented in the url
check if the address is correct

The machines also have not trouble accessing standard files shared on the server through a map network drive.

Well quite simply that means there is a networking error in the setup of those 2 machines. Check the DNS settings of a machine that works against those 2 - there is likely to be some difference...