Details
If you attempt to delete more than five virtual machines at once from the Datastore Browser, the ESX Server connection through the VI Client fails and you will be prompted to log in again.
This issue occurs only when connected directly to the ESX Server host through the VI Client.
Solution
Delete virtual machines from the Datastore Browser one or two at a time when connected directly to the ESX Server host.
Alternatively, connect to VirtualCenter Server through the VI Client, select the host, and delete the virtual machine from the Virtual Machines tab. This issue occurs only when connected directly to the ESX Server host through the VI Client. Multiple virtual machines can be deleted from the Datastore Browser when connected to the VirtualCenter Server.
Based on VMware KB 1003250
