Hi,
Here is safe steps that you can follow.
1. Take one ESXi host, migrate all the VM out of it to other ESXI host.
2. Disable VAAI as per this http://kb.vmware.com/selfservice/documentLinkInt.do?micrositeID=&popup=true&languageId=&externalID=1033665
3. Then migrate only one VM back to this ESXI host.
4. Try cloning of this VM.
Yes, reboot not needed.
Regards
Mohammed