Problem with Vista in VMWare Server

I have 4 Virtual Machines on my VMWare Server.

1. Windows 2000

2. Windows 2003

3. Windows XP

4. Windows Vista

I am using the VixCOM COM control to communicate with the server.  They are all running the same script, but when I try to copy files onto the Windows Vista VM using CopyFileFromHostToGuest, it returns VIX_E_UNRECOGNIZED_COMMAND_IN_GUEST.  I have the VMWare Tools installed on the VM, the account on the VM is an administrator, and UAC is turned off, so I don't know why it works on all the other OSes, but not Vista.

When setting up the VM, VMWare Server said that Vista was "experimental".  Could this be why the function is not working?

Thanks