Check the Oracle installs and make sure your TNSNames configuration is the same.

Also, since you copied a virtual machine, make sure there is not a DNS conflict of some sort. Oracle clients can be sensitive about IP and MAC addresses. Make sure you don't have something dumb like the clone has the same IP address as the original machine.

I would assume they are on the same subnet, but if you clone was moved to another subnet you may have a transport error happening - you may want to use IP addresses in your TNSNames configuration.