I have a domain name that can be reference as www.domainname.com or domainname.com. Users started complaining about extremely slow response times. When I pinged www.domainname.com, I noticed that the IP address is not the correct IP address. When I ping domainname.com, the IP address is correct. How can I fix this?

There can be a problem with the DNS.
Check all your A Records and make sure they are pointing to the same IP.

Also as a precaution, go into your Cobalt control panel and check the settings of the site.

Make sure host is: www.
domain: domain.com
email server: domain.com