"A specified parameter was not correct" Error in the VI Client Interface When Trying to Power On a Virtual Machine (2173)
This error occurs because disk space is low on your datastore where the virtual machine is located. During power on, enough space must be available to store the swap file associated with the virtual machine. Typically, this is equal in size to the amount of memory allocated to the virtual machine. A large-memory virtual machine (that is, a virtual machine allocated 4GB of RAM) requires 4GB of free disk space on its datastore in order to power on.
For information on a similar error message reported in vCenter Server 4.x, please reference Powering on a virtual machine fails with the error: memoryAllocation.reservation (1036914)