I found the process I had used previously. Here it is here. Summarized below.
Make sure the VM in question is shutdown.
From the console
xe vm-shutdown uuid=<UUID of Your VM>
xe vbd-list vm-uuid=<UUID of Your VM> params=uuid,type
xe vbd-destroy uuid=<UUID of Your CD/DVD> Of critical importance do not select Disk, ensure you select the UUID of the cd
Repeat step 4 as many times as you have CD's that are unusable.
Reboot the VM and add the device again.