VMotion stops at 78% with the error "A general system error occurred: Source detected that destination failed to resume"

This error message indicates that the shared storage is not available equally to both host involved in the VMotion event.

Remove the volumes involved from the ESX hosts and re-add them by using the exact same host names to solve this problem. You will have to svmotion VMs off this volume before doing this. If you're using NFS based storage this can be done directly from the Storage configuration, but if you're using block based storage (FC/iSCSI) you should rather use LUN masking and hba rescanning.

This problem has been observed when using NFS based storage and the volumes were mapped with non-consistent nfs-hostnames (fqdn/non-fqdn/ip address).

Yes, I really hope this was an NFS volume. Folks, if you experience this with a VMFS volume, do not try to remove the volume by right clicking it. That will destroy the VMFS volume. Be careful about what you tell peaople, Lars ;)