SQUID v. 2.3 Stable4

I am running Red Hat 7.0 with Squid for internet access. Their are maybe 7 users total using it. This has been running for a year without incident until a month ago. We can not get out to web sites, like www.msn.com. It comes up saying “Unable to determine IP address from host name for www.msn.com ”
Also:
The dnsserver returned:

Name Error: The domain name does not exist.
This means that:

The cache was not able to resolve the hostname presented in the URL.
Check if the address is correct.

I am not sure what is going on but any suggestions would be appreciated.