Alrighty I have found the issue :smileyhappy:
Apparently the virtual machines had been snapshot at some stage and although the snapshots had been removed the vmx file still needed to have the CTK variables removed.
As below :smileyhappy: I hope this helps someone as I wasted a heap of time on this.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1013400
To remove CTK variables from the .vmx file:
1.Log into to the ESX service console.
2.Power off the virtual machine.
3.Unregister the virtual machine from the vCenter Server Inventory by right-clicking the virtual machine and clicking Remove from Inventory.
4.Open the .vmx file in a text editor.
5.Locate variables similar to the following and delete the entire line:
scsi0:0.ctkEnabled = "true"
ctkEnabled = "true"
Notes:
•If there is more than one virtual disk, there are additional scsi#:#.ctkEnabled entries. These must be removed as well.
•You may also find ide#.#.ctkEnabled entries. These must be removed as well.
7.To guarantee that change block tracking cannot be enabled, add the following line to the configuration file:
ctkDisallowed="true"
8.Open the datastore browser and change to the directory where the .vmx file is located
9.Right-click the .vmx file and click Add to Inventory.
10.Save and close the file.
11.Reboot the virtual machine to apply the changes.