Is this a DNS Problem

I have a problem getting to some site on the net from our network, even though they exist. But if I use a search engine and try getting there through the search engine it works fine. I then use the “whois” from network solution and discovered that the site is hosted by a domain name with domain.co.uk while the site address is domain.com. Doing a “tracert” using the domain name will also return a site unreachable error, but if the IP address of the domain is used it works fine.