DNS Issues

Hello,
I have an issue where a user has an IP address that is different from my DNS forward lookup and nslookup. If I use the IP from the user machine I can ping but not with the computer name. When I use the computer name I get the DNS IP and is unreachable. nslookup also shows the incorrect IP. DNS and nslookup match but the ipconfig on the users machine is different. What could possible be happening?

Thank you for your help.

The IP address you have is old. Try an ipconfig /flushdns.
If that doesn't work, find out which DNS server (eg, your router or domain controller) is giving you the wrong information and found out why it hasn't updated.