A few things will cause this for sure - could be others but check these to start:
Firewall ports - make sure your cells can talk freely to each other, all ESX hosts, and all vCenters.
TimeSync - the cells need to be withing 2 seconds of each other on time or you will get some really bad slowdown on some operations.
DNS - make sure all ESX hosts, vCenters, and cells can resolve each other forward and reverse lookup via DNS.
Transfer space access - make sure /opt/vmware/vcloud-director/data/transfer is Owned by vcloud:vcloud on each cell and they point to the same shared storage. If one shows something off it will cause issues.
Hope this helps, if not please let us all know if you find the answer so we know what else to watch out for.