MarVista wrot
your both host are on ESX 5.1 and v center 5.1? Because only with vmware 5.1 you can migrate vm without shared storage as it has enhanced vMotion feature.
Yes, boths hosts are 5.1 and vCenter is 5.1. I have tested this on a different set of ESXi boxes in the same vCenter and it worked fine.
to checking this issue you can try vmotion with shutdown the vm for time being.
Doing a cold migration would defeat the whole purpose of testing / verifying that a VMotion between 5.1 hosts works ok.