Vmware Server: Datastore Browser could not successfully retrieve data from the server

One possible cause is that the folder containing VMs is not accessible when vmware daemon is started.
After checking that the folder is now accessible, restart vmware daemon:
/etc/init.d/vmware restart

If it fails, try:
Select datastore in question
Click Commands > Refresh Datastore

If it fails, try the following:
1) re-Add VM, or
2) re-create datastore