domain name resolution
 

How long does it usually take for a domain name to resolve once you change nameservers.

couple hours nowadays...about 4 hours

Yeah shouldn't take longer than 24 hours. Sometimes it even takes less than 30 minutes.

So is that my problem, I've been trying to add it in cpanel for the last 3 hours.

Sorry, the domain is already pointed to an IP address that does not
appear to use DNS servers associated with this server. Please transfer the domain to
this servers nameservers or have your administrator add one of its nameservers to /etc/ip.remotedns and make the proper A entries on that remote nameserver.
/n

maybe you setup DNS with the company you registered the domain name at and forgot it's pointing somewhere else? all you gotta do is delete the entries in your registrar.....

Shouldnt be longer then 24 hours.

about 2 to 4 hours nowadays. used to be 24 to 48